Review Incident Shin.. - authority for electricity regulation, oman

Review
Incident Shinas area 27-29 August 2007
Final Report
for
Authority for Electricity Regulation, Oman
Submitted by
Bonn, Germany/Arnhem, Netherlands
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Executive Summary
On 27 August 2007, at 22.07h a fault on the 132 kV-line of the Oman Electricity Transmission
Company SAOC (OETC) from Wadi Jizzi to Shinas led to an interruption of the power
supply in the Shinas area. This area was completely without power until 07.35 h the following
day, when the supply was partly restored via the 33 kV feeders of Majan Electricity
Company SAOC (MJEC) using a rota load shedding scheme. The Shinas 132 kV grid station
was energized again by OETC at 23.55 h on 28 August 2007. After that MJEC restored
the supply to all customers, which was completed at 01.34 h on 29 August 2007.
The Authority for Electricity Regulation, Oman (the Authority) asked KEMA to identify the
technical reasons for the interruption and investigate the overall management of the incident
by OETC. The Authority is of the view that the time taken by OETC to restore supplies
was unduly excessive.
We have studied several documents, including the incident reports/sequence of events of
both OETC and MJEC. Furthermore, we have interviewed representatives of both OETC
and MJEC, including both General Managers, OETC’s maintenance manager, representatives
of OETC’s Load Dispatch Center and responsible people on-site, such as OETC’s operation
engineer and MJEC’s local staff in the Sohar area.
The conclusions of our review can be summarized as follows:
the duration of the outage was influenced by a number of factors: the most important
being that the Wadi Jizzi – Shinas line was not (n-1) compliant as required by Oman
Transmission Security Standards and international best practice;
OETC was aware the Wadi Jizzi – Shinas line was not (n-1) compliant but did not have
a comprehensive plan in place to detect faults. Fault distance indicators installed at the
Wadi Jizzi grid station could have reduced the time taken to locate the fault and reduce
the duration of the supply interruption;
Since we have only seen an expired maintenance contract, we are unable to confirm
that a maintenance contract for the Wadi Jizzi – Shinas line was in place at the time of
the incident;
spare parts were not immediately available on site and had to be transported from remote
locations. This contributed to the supply interruption being longer than necessary.
The fault was located at 1.00 am whereas spare parts arrived on-site at 4.30 pm. Some
14 hours was lost by not having spare parts available close to the site;
organization of the emergency response effort was ad-hoc and poorly organized - it was
not always clear who was in charge for coordinating the restoration activities and some
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necessary safety measures such as line earthing in both the Wadi Jizzi and the Shinas
grid stations were not immediately implemented. OETC did not have a complete set of
defined System Normalisation procedures and System Incident procedures in place as
required by the Grid Code of Oman (OC 7, Contingency Planning Code, version 1.000).
Restoration time could have been significantly reduced if appropriate procedures had
been in place;
We recommend that:
OETC expedite the construction of a second circuit to Shinas to secure n-1 compliance;
immediate implementation of the Contingency Planning Code of the Grid Code;
further development of LDC procedures, and immediate implementation of the already
identified training procedures and training plan;
OETC include special measures (such as manual re-closing) for non-(n-1) compliant
lines in dedicated procedures;
Develop special arrangements with the Royal Oman Police for emergency situations;
KEMA’s assessment has identified serious problems in the preparation for and the handling
of the incident by OETC management. We believe it is fair to say that the impact of the incident
could have been limited to a significant extent if proper preparation was in place and a
more prompt and adequate response had followed. Our review reveals a significant scope
for improvement to be achieved in future in order to bring the quality of operations within
OETC to a level in line with what could reasonably be expected from a transmission operator
operating within the Oman electricity market.
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TABLE OF CONTENTS
1. Introduction 5
2. Before the incident 6
2.1. Network.............................................................................................................. 6
2.2. Preparedness for a fault in the Wadi Jizzi – Shinas line ..................................... 7
2.2.1. Shorten the time for finding the fault .............................................................. 8
2.2.2. Spare parts available..................................................................................... 8
2.2.3. Repair Tools available ................................................................................... 8
2.2.4. People available ............................................................................................ 9
2.2.5. Maintenance Contract ................................................................................... 9
2.2.6. Conclusion..................................................................................................... 9
2.3. System Operation ............................................................................................ 10
2.4. Emergency organization .................................................................................. 11
3. Incident 12
3.1. Immediately before the incident........................................................................ 12
3.2. Immediately after the incident .......................................................................... 12
3.3. Looking for the fault location ............................................................................ 13
4. Repair of the Fault and Restoration of Supply 14
4.1. Fault location.................................................................................................... 14
4.2. Evaluation of the damage................................................................................. 14
4.3. Spare parts ...................................................................................................... 15
4.4. Police reporting and rest .................................................................................. 15
4.5. Repair of the line.............................................................................................. 16
4.6. Incident center ................................................................................................. 17
4.7. Restoring energy supply via back-feeding........................................................ 17
4.8. Restoring energy supply after repair ................................................................ 18
5. Conclusions 19
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1. INTRODUCTION
On 27 August 2007, at 22.07h a fault on the 132 kV-line of the Oman Electricity Transmission
Company SAOC (OETC) from Wadi Jizzi to Shinas led to an interruption of the power
supply in the Shinas area. This area was completely without power until 07.35 h the following
day, when the supply was partly restored via the 33 kV feeders of Majan Electricity
Company SAOC (MJEC) using a rota load shedding scheme. The Shinas 132 kV grid station
was energized again by OETC at 23.55 h on 28 August 2007. After that MJEC restored
the supply to all customers, which was completed at 01.34 h on 29 August 2007.
The Authority for Electricity Regulation, Oman (the Authority) asked KEMA to identify the
technical reasons for the interruption and investigate the overall management of the incident
by OETC. The Authority is of the view that the time taken by OETC to restore supplies
was unduly excessive.
We have studied several documents, including the incident reports/sequence of events of
both OETC and MJEC. As background documents we used the Grid Code (vs. 1.000) and
the ‘Report on capital and operating expenditure requirements for the Oman electricity
transmission company for the period 2006 - 2010’ 1 .
Furthermore, we have interviewed representatives of both OETC and MJEC, including both
General Managers, OETC’s maintenance manager, representatives of OETC’s Load Dispatch
Center and responsible people on-site, such as OETC’s operation engineer and
MJEC’s local staff in the Sohar area.
This document reviews the event largely in chronological order. We start with a review of
the situation before the incident took place (chapter 2). After that, we review the activities
during and immediately after the incident in chapter 3. Chapter 4 covers all the restoration
and repair activities. Our concluding remarks are contained in Chapter 5.
1 by SKM for AER, July 2006
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2. BEFORE THE INCIDENT
In this chapter we discuss the status-quo of the network, organization and staff in relation to
the incident. Therefore we are reviewing whether OETC was properly prepared for the fault
and its consequences.
2.1. Network
The 132 kV Shinas grid station is connected to the Main Interconnected System by one
single-circuit 132 kV-line, coming from Wadi Jizzi. In the Shinas grid station two 63 MVA
132/33 kV-transformers feed the 33 kV-network Shinas operated by MJEC. This 33 kVnetwork
has interconnections to other 33 kV networks of MJEC. These connections provide
a limited back-feed via the underlying 33 kV-network. However, the back-feed is only available
after rearrangements of the 33 kV-network and load-shedding in the Shinas area and
elsewhere. Therefore the 33 kV-network only provides limited redundancy in the event of
the single-circuit 132 kV-line tripping. It can therefore be concluded that the supply to the
Shinas 33 kV network does not meet the Security Standard criteria of (n-1).
According to the (proposed) Oman Transmission Security Standards 2 , demand groups of
20 to 100 MW should be restored immediately after a first outage ((n-1) Security Standard).
Since the load of the Shinas network can reach 65 MW (forecasted load for 2007) loss of a
single line, which has to be repaired before the load can be restored, does not meet these
Security standards.
The (proposed) Security standards in Oman are similar to Security standards in many Grid
Codes. However, in contrast to the Oman Transmission Security Standard, some grid
codes and/or design standards accept losing load if it is only for automatic or manual
switching activities taking a few minutes. E.g. the GB Security and Quality of Supply Standard
specifies that for interruptions of loads (‘group demands’) up to 60 MW, two-thirds of
the load has to be restored within 15 minutes. Nevertheless, since there are no possibilities
to quickly restore the load in the Shinas area by fast switching actions, the network design
would also not have met this type of standard.
2 See section 6.2 of the ‘Report on capital and operating expenditure requirements for the
Oman electricity Transmission Company for the period 2006 - 2010’, by SKM, July 2006.
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We were told that the investment in a second circuit to the Shinas grid station was already
planned during the time that the Ministry of Housing Electricity and Water was the operator
of the transmission network, ie there were plans for a second circuit to Shinas before 1 May
2005 3 . According to OETC’s investment plan for 2006 4 a second 132 kV-circuit to the Shinas
grid station had been planned for construction in 2006. We understood from OETC 5
that this project had been delayed because it was combined with the investment in a new
grid station in Liwa, which increased the efficiency of this investment. OETC confirmed that
the construction of a second circuit to Shinas is now in the tendering phase. However, we
have not seen any proof of this.
It can be concluded that if there had been a second 132 kV-circuit to Shinas, the fault would
not, under normal operating conditions, have caused an outage since the second feeder
would have been capable of supplying the entire load. For the peak demand of the Shinas
area (65 MW forecasted for 2007) this situation is unacceptable according to international
and Oman standards. This has been recognized by OETC and its predecessors for many
years (before 2005) and KEMA strongly recommend that the contract to provide for n-1 is
implemented on an expedited basis.
2.2. Preparedness for a fault in the Wadi Jizzi – Shinas line
The reason why, in general, the (n-1) criterion is applied is that there is a reasonable risk
that faults in lines, transformers, generators etc will occur. This risk combined with the
damage of losing load results in the need to invest to provide additional redundancy of system
elements e.g. lines, transformers etc. Security Standards allow for and even require
large investments to provide (n-1) security in transmission networks.
Following this logic, situations in which these standards are not met should be considered
very seriously. For these situations in which a single fault will lead to an outage with significant
loss of load for a long duration (the repair time) there should be detailed and comprehensive
plans.
Since it was recognized by OETC (see section 2.1) that the (n-1) security criterion was not
met for the Wadi Jizzi – Shinas line, then there should have been a plan in place to deal
3 1 May 2005 is the date OETC took over the responsibility of the transmission network.
4 See section 7.2 of the ‘Report on capital and operating expenditure requirements for the
Oman electricity Transmission Company for the period 2006 - 2010’, by SKM, July 2006.
5 Interview on 1 September 2007.
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with the actual situation that arose here. The fault in this line, which led to an outage of a
load of up to 65MW, was far from being a non-credible event. The objective of this plan
should be to limit the customer outage until the circuit can be repaired and restored.
The plan for such a fault should concentrate on minimizing the duration of restoration or repair.
This includes several issues described below.
2.2.1. Locating the Fault
We understood that the operation engineer did not have a very detailed indication 6 about
the distance of the fault from the Wadi Jizzi grid station. Appropriate fault locators could
have been installed in the Wadi Jizzi grid station to assist the operation engineer to locate
the fault more precisely and provide the patrolling crew with a smaller area to search for the
fault. This would have shortened the time for finding the fault location (in this case 2.5
hours) significantly.
2.2.2. Availability of Spare Parts
Repair time of a line can be considerably reduced if all relevant spare parts are available in
good quality, quantity and close to the line. Moreover, transportation would be available as
well. We understood that spare conductors and sleeves were available at OETC, but that it
took a) time to find them and b) time to transport them because a border station had to be
passed. Spare insulators were not available at OETC at all. However, they were provided
by Civil Co 7 . Having all spare parts available within a limited distance of the event would
have reduced the time for getting spare parts to the fault location (in this case about 14
hours) significantly.
2.2.3. Repair Tools available
We understood that maintenance contractor Civil Co has no crimping tools locally available
for repairing the faulted 175 mm 2 conductors. Although not on a critical time path in this incident,
the same requirements for these tools apply as for spare parts. They should be available
in good quality, quantity and close to the line. According to the expired maintenance
6 The site-engineer assumed that the distance relay tripped in zone 1, which means that the fault should be
somewhere between 0-80% of the line length from Wadi Al Jizzi.
7 It has to be noted that in this incident there was no need to replace the poles, since they were all intact. Since
this review is about this incident only, we have not gone into detail about the availability of or repair of poles.
We note however that in the event of a broken pole, the repair would be far more complicated and lengthy than
in the current incident.
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contract with Civil Co (we have only seen a version valid until 26/05/2007), necessary
equipment, tools and instruments are to be provided by the contractor (see section 2.2.5).
2.2.4. People available
For both patrolling and repair of the line, the same applies as for spare parts and repair
tools. They should be available in good quality, quantity and close to the line.
We understood that the line crew of OETC started patrolling half an hour after the fault,
which means that they were readily available. Moreover, another patrolling crew was offered
by MJEC and assisted OETC with patrolling. However, this was on an ad-hoc basis
and not as a result of any plan by OETC.
Repair of the line should be organized in such a way that the work order can be issued
without delay. Preferably this should be done either by own personnel or under a (maintenance)
contract (see section 2.2.5).
The operation engineer of OETC on site had to coordinate patrolling, fault investigation,
looking for spare parts, repair, safety switching and communication with police and MJEC,.
He was the only person that was authorised to close and open earthing switches in grid stations
as well. In our opinion the operation engineer is in the case of a fault overloaded with
activities, which could negatively influence the duration of the supply interruption.
2.2.5. Maintenance Contract
We have not seen the actual maintenance contract with contractor Civil Co and are unable
to confirm that a maintenance contract was in place at the time of the incident. However, we
received a copy of the contract that was valid until 26/5/2007. This maintenance contract
covered emergency maintenance of 132 kV lines, including the provision of adequate qualified
and experience staff for this purpose with all necessary equipment, tools etc. in order to
carry out the maintenance and attending the emergencies in an effective manner. The contract
specifies emergency maintenance for woodenpole structures specifically. The specification
includes the replacements of broken insulators and making of mid span joints and
restringing of broken and damaged conductors. However, the responsibility for the provision
of spare parts is with the OETC, although collection of the materials is at Civil Co again.
2.2.6. Conclusion
It can be concluded that due to the fact that spare parts and repair tools were not readily
available, the interruption had a longer duration than necessary. If we consider that the fault
location was known at 01.10h on 28 August and that the latest spare parts arrived on-site at
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16.30h on 28 August, it can be concluded that a lot of time (about 14 hours) was lost by not
having spare parts available close to the site.
Moreover, the time of finding the fault could have been shortened by having the right
equipment in place for estimating the fault location more correctly. Compared to the previous
item this issue is limited but we believe that a reduction in the search time of 2.5 hours
could have been achieved.
Finally, OETC had enough people on-site but this was partly because MJEC offered OETC
assistance. Although we support the assistance provided from one company to another, it
has to be noted that in this case it was done on an ad-hoc basis and therefore not planned.
This means that OETC was fortunate in this instance to get this support from MJEC but we
would caution against relying on this kind of support in future.
2.3. System Operation
The system is operated from the Load Dispatch Center (LDC) of OETC in the Muscat area.
This LDC is equipped with a modern SCADA system 8 . This means that the operators can
see the status of switches and measurements on their screens and operate circuit breakers
and disconnecting switches. Earthing switches were not controllable from the control center
at the time of the incident 9 .
We have received a set of procedures from the control center. Relevant procedures include
‘OETC Procedures during Abnormal Operating Conditions’ and ‘Restoration of the Power
System following a complete or partial “Black-out”’. Unfortunately the set of procedures is
not yet complete.
Since it is recognized (see section 2.1) that a single outage in the line Wadi Jizzi to Shinas
could lead to a complete outage of the Shinas area (up to 65 MW) for a considerable period,
we would have expected that plans would have been in place to deal with a permanent
outage in this non-(n-1) compliant line 10 . However, this was not the case.
8 ABB Spider system
9 We learned that originally the earthing switches were controllable from the SCADA. However, because of
safety reasons it was decided to only operate earthing switches locally. Although there are also reasons why
earthing switches should be operated remotely, this approach is not unusual in transmission networks.
10 And probably other non-(n-1) compliant lines. However, this is not part of this review.
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One set of procedures is about training for control center staff. These procedures include a
road map for training, plans for training and a content list for training, including training for
emergency situations. However, training has not started yet. This appears to be due to a
lack of manpower for system operation. This means that control center staff were not adequately
trained for this kind of event. However, as we point out later, in this incident this did
not significantly affect the duration of the interruption.
2.4. Emergency organization
In case of an emergency, it is the practice within OETC that the Head of Maintenance will
be the high-level coordinator. He will contact the manager of transmission and maintain
contact with the operation engineer. The Load Dispatch center communicates with the directly
connected customers and with the control centers of the distribution companies. Distribution
companies deal with their customers.
OETC does not have a complete set of defined System Normalisation procedures and System
incident procedures in place as required by the Grid Code of Oman (OC 7, Contingency
Planning Code, version 1.000).
The consequence of that is that OETC relies completely on experience and ad-hoc measures.
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3. INCIDENT
3.1. Immediately before the incident
At 22.00 h the load of the Shinas region was 51 MW. At this time the system was stable.
Moreover, no trips because of humidity were taking place 11 .
3.2. Immediately after the incident
At 22.07 h the 132 kV Circuit breaker of the Wadi Jizzi to Shinas line opened because the
distance relay at Wadi Jizzi operated. Since the Shinas 33 kV-network is only supplied by
this line, the trip led directly to the interruption in the power supply of this network. The reason
for the trip is not yet known.
The SCADA system informed the staff of the Load Dispatch Center immediately and provided
the information that a distance relay in the Wadi Jizzi grid station had tripped. From
the Shinas grid station no indication was received.
At 22.08 h the 132 kV Circuit breaker of the Wadi Jizzi to Shinas line reclosed automatically
and tripped again at Wadi Jizzi.
Because the staff of the Load Dispatch Center considered humidity as a likely cause, they
decided to manually reclose the circuit breaker at 22.22 h. This is not a normal procedure,
but taking into consideration a loss of load of the Shinas area and having the experience
that 90% of the faults in this region are caused by humidity the LDC staff took the risk of an
additional reclosure. The distance relays operated again to trip the circuit 12 .
We can understand the logic applied by the LDC staff to reclose the line manually, but we
note that reclosure of lines after a fault is not without risk for people and equipment. Although
nothing severe happened as a direct result of these auto-reclosures, it would be
11 Humidity combined with fine dust is causing lots of trips in the 132 kV system at present. However, during
the evening of the event no trips of this type were recorded.
12 The sequence of events of MJEC reports that at 23:36h there was another attempt to manually close the 132
kV Circuit breaker of the Wadi Jizzi to Shinas line, again without success. OETC reports do not mention this
third attempt to reclose the Circuit Breaker.
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crucial for the LDC staff to be backed with appropriate procedures (eg an agreed re-closing
policy) in case something serious had happened.
The LDC informed the operation engineer, MJEC and OETC’s head of maintenance immediately
after the fault. Moreover, the LDC asked MJEC at 24.00 h whether back-feed would
be available via 33 kV-lines. The answer was negative: MJEC did not have back feed available.
3.3. Looking for the fault location
The only indication for fault location available was the distance relay in the Wadi Jizzi grid
station. However, for unknown reasons, this relay did not provide a proper fault indication.
Based on his experience, the operation engineer concluded that the fault had to be in zone
1, which meant the first 80% of the line, starting from Wadi Jizzi.
Two patrolling teams started patrolling the line at about 22.40 h. The first patrolling team
was an OETC/Civil Co team. Civil Co is providing patrolling services under the (expired)
maintenance contract (see section 2.2.5). The other patrolling team was offered by MJEC
to OETC. The patrolling teams were instructed to start looking for the location from tower
88. One team in the direction of tower 1, the other in the direction of tower 231 (80% of the
line).
After about 2.5 hours, the fault location was found at 01.10 h on 28 August. OETC was
happy with the time for getting the fault location, taking into account the length of the line
(37 km) to be patrolled, the darkness and the terrain that had to be patrolled. Although we
do not have a complete overview on the terrain that had to be patrolled, we did not find any
indication that this time was too long, taking into account that no fault distance indicators
were installed at the Wadi Jizzi grid station (see section 2.2.1).
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4. REPAIR OF THE FAULT AND RESTORATION OF SUPPLY
4.1. Fault location
The fault itself consisted of three broken conductors and several broken insulators 13 . The
three conductors were cut above a graded road, close to Sohar roundabout, which is part of
the highway system of Oman. The fault location itself is flat with not many obstacles. The
line was cut between tower 165 and 166 and isolators of towers 165, 166 and 167 were
broken. Poles 165 and 166 are constructed with two wooden poles (H-poles). Tower 167 is
a wooden three-pole suspension tower and was assumed (by OETC) to have absorbed the
forces.
Figure 1: Fault location. (Left: Pole 165 and 166 with graded road in between. The line was
cut exactly above the road. Right: suspension tower 167).
4.2. Evaluation of the damage
After locating the fault, the operation engineer went directly to the site. He investigated the
fault and at 02.30 h the information was available about the spare parts that would be
needed for the repair. It was also recognized that these spare parts were not available in
the Sohar area.
13 The cause of the fault itself was not a part of this review. We therefore do not go into detail on this.
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4.3. Spare parts
Since spares were not available in the Sohar area, spare parts had to be found in other regions.
It was recognized that in the network around Al Buraimi similar lines are installed as
the faulted line. For this reason, at 02.30 h OETC staff in Al Buraimi was contacted by the
operation engineer. The Al Buraimi staff were asked whether they had spare parts for the
line in stock. At 03.30 h the Al Buraimi people reported that they had conductors and
sleeves available. However, they could not find any insulators in their stores.
Although only two to three hours drive (with this material, with a normal car less than two
hours) from the fault location, it took until noon before the material was on the fault location.
Main reason for this was that a border station (Although in Oman, Al Buraimi is on the UAE
side of border check point) had to be crossed. For crossing the border, a special permission
had to be issued by the Royal Oman Police (“ROP”). However, this could only be done during
office hours. The Al Buraimi OETC employee therefore went to the ROP at around
07.30-08.00 h. With some difficulty (he had to leave his passport behind as guarantee) he
managed to get permission but not until around 10.00 h. Only after this time could the conductors
and sleeves have been transported out of Al Buraimi. Conductors and sleeves arrived
at the fault location at about 15.00 h. We do believe that it would be very useful to develop
special arrangements with the ROP for emergency situations, which will enable a
smoother restoration of the faults in case of emergency.
With respect to the insulators which were not available at Al Buraimi, OETC tried to contact
KEC and Civil Co for insulators. In the end, Civil Co found six insulators in their stores
which were left over from the time they constructed the line. However, it took a long time to
find these spare parts and transport them to the fault location. All material was at the fault
location at 16.30 h.
It is recognized by the Head of Maintenance of OETC that it took too long to get the spare
parts to the fault location. For this reason OETC will in future store spare material in the
Sohar area. This will include 10 insulators, sleeves and conductors.
4.4. Police reporting and rest
Between 02.30 h and 04.30 h the operation engineer went to the police to report the incident.
After that (between 04.30 and 05.30h) the operation engineer went home for a short
rest of about one hour.
We recognize that both reporting to the police and resting were probably necessary actions
that had to be performed by the operation engineer. However, we recognize as well that it
was unclear who was in charge for the coordination of the restoration activities at that time
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at site. Moreover, necessary safety measures such as line earthing in both the Wadi Jizzi
and the Shinas grid station were not yet in place. It could be concluded that the coordination
at the fault location was a one-man organization. Especially during the first hours additional
staff could have relieved the operation engineer.
4.5. Repair of the line
Since no maintenance contract for these kind of emergency repair activities was in force at
the time of the fault (see section 2.2.5), Civil Co was contracted for the repair activities at
06.30h. A repair crew, consisting of Civil Co people was on-site at 08.00h. This crew was
instructed not to touch the line, since the line was not yet earthed. At 11.20 h the line was
earthed at the Shinas grid station by the Operation engineer (PTW#400). At that time, the
earthing switches at the Wadi Jizzi grid station were closed as well by local staff. After the
line was earthed and the portable earths installed at the site of the fault, the preparation activities
for the repair had been started.
However, it was only when all material was available on-site that the real repair activities
could start. It was reported by different people that conductors and sleeves arrived from the
Al Buraimi substation around noon. The insulators arrived at about 16.30 h.
The repair activities itself consisted of the replacement of a number of insulators 14 and three
stretches of conductors (one on each phase). These activities took from 16.30h to 23.35 h,
which means about seven hours. Taking into consideration that the construction crew was
already on-site for the entire day and that the majority of the work was done in darkness
and with material which was not familiar to the repair crew, a repair time of seven hours
could be considered reasonable.
At 23.35 h the repair work was completed. At this time the operation engineer was at the
Shinas grid station for opening the line earth switches and closing the line disconnectors.
He performed these switching activities after OETC management on-site confirmed to him
by phone that the repair activities had been completed, portable earths had been removed
and that the line could be energized again. At the same time, the earths at the Wadi Jizzi
were removed by local grid station staff.
14 Different people mention different numbers from three and five.
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4.6. Incident center
As discussed in the section 2.4, OETC does not have procedures for an emergency organization.
However, OETC’s Head of Maintenance was in charge of the restoration activities.
He was doing this from his offices in Muscat. The General Manager of Muscat was on-site
from early morning onwards in order to take decisions. Moreover, the operation engineer of
OETC in this area was coordinating the local activities. This included coordination of line
patrolling, analysis of the damage, looking for spare material (e.g. contacting the people at
Al Bahraimi substation, at contractor Civil Co, at KEC), communication to local people from
distribution company MJEC, communication to the police, earthing of the line at the Shinas
grid station, repair activities, releasing the line for energizing, opening the earthing switches
at the Shinas grid station.
Although the Grid Code (OC 7.6) requires the establishment of an incident center immediately
following a major System Incident, OETC did not do so. Instead of this, a number of
people, including the General Managers of OETC and MJEC gathered at the location of the
fault.
We do think that the provisions in the Grid Code to establish an incident center are sensible
rules that could improve communication and coordination.
4.7. Restoring energy supply via back-feeding
The Shinas 33 kV network has two long 33 kV-connections to the Sohar 33 kV-network
which allow for limited back-feeding. At about 07.30h MJEC started to restore customers
(up to 30 MW could be restored) on a rota basis. For this, MJEC had also to shed load in
other regions, by switching off 11 kV-feeders (max 25 MW was shed, it was taken care that
the load of hospitals, communication points and police was not shed). By this scheme,
more customers were interrupted but the damage was shared between more customers.
Because of the long 33 kV-connections (up to 70 km) and the power factor of the load of
(mainly) air conditioners, maintaining the Voltage was an important issue. For this reason,
MJEC had sent staff to important 33 kV substations in order to be able to control the
capacitor banks and the tap changers on the 33 kV-transformers manually (normally operated
automatically).
We have asked MJEC why they only started restoring the energy supply at 07.30 h. MJEC
explained that only then did OETC inform MJEC that the incident was larger than they had
indicated before. At around 09.00 h OETC informed MJEC that the outage would take to
about 16.00 h. However, it took until 23.55h.
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At 14.45 h LDC asked the Oman Mining Company to provide assistance by synchronizing
their GTs to the 66 kV network. After that MJEC was informed to take whatever possible
load from the Magan 66 kV substation. Although a positive action, we are a bit surprised
about the timing of this action, 16 hours after the start of the incident and more than seven
hours after restoration by MJEC had started.
4.8. Restoring energy supply after repair
After the transformers were re-energized, MJEC could restore the supply in the Shinas 33
kV again, by rearranging the 33 kV network. Since the 33 kV-feeders are not (yet) in the
SCADA system, this job was carried out by five groups of MJEC staff. At 01.34 h all customers
were back on supply.
Considering the size of the network and the length of the feeders (up to 70 km), the fact that
the MJEC network was rearranged for rota supply to different customers and the darkness,
restoration of the supply to all customers in 1 hour and 44 minutes can be considered as a
good performance on the part of MJEC.
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5. CONCLUSIONS
Based on the review described in the previous chapters we conclude that the duration of
the outage was influenced by a number of factors:
The first and most important factor is that the supply to the Shinas area is not (n-1) compliant.
If the supply had been (n-1) compliant the permanent trip of a single circuit would not
have led to any supply losses for customers. Although the network should have been redundant
according to the standards in Oman and international best practice, the process is
well underway with the project to provide this redundancy in the tendering phase.
Since it was recognized by OETC that the line was not (n-1) compliant and because a line
fault is not uncommon, we would expect proper preparation including a comprehensive
plan for a line fault in the Wadi Jizzi – Shinas line.
With respect to this preparation, fault distance indicators installed at the Wadi Jizzi grid
station could have reduced the time for locating the fault location (2.5 hours) significantly.
Since spare parts were only completely available about 14 hours after the materials that
were needed for repair of the line were identified, we conclude that spare parts were not
available or not available on a limited distance to the line. Having relevant spare parts
available would have reduced this time of 14 hours significantly.
Since we have only seen an expired maintenance contract, we are unable to confirm that a
maintenance contract for the Wadi Jizzi – Shinas line was in place at the time of the incident.
We found some issues which did not influence the duration of the outage significantly but
could also be improved. Firstly, we found that OETC relied on the assistance of other parties,
e.g. a team from MJEC assisted the line patrol team on an ad-hoc basis. Plans for incidents
of this type should include formal arrangements for assistance from third parties.
The organization of the emergency organization was ad-hoc. We do suggest developing
and using clear procedures for organizations of emergency situations as proposed by
the Contingency Planning Code. This includes system normalization procedures and system
incident procedures. Moreover, it includes the establishment of an incident center, a
communication plan and the organization of the restoration and repair, including the
role and workload of the operation engineer and coordination of the outage. Finally, we do
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elieve that it would be helpful to develop special arrangements with the Royal Oman Police
for emergency situations, which will enable a better cooperation and understanding in
case of emergency.
Although a start the procedures of the LDC should be further completed and developed.
The training procedures and training plan are rather complete but the training for
LDC should actually take place.
Since a fault in a non- (n-1) compliant line is a special case, sometimes unusual measures
(such as manual reclosing) could be considered. However, since there is limited time to
evaluate these measures, we suggest including special measures for non-(n-1) compliant
lines in dedicated procedure. This could include a re-closing policy especially as the
network is subject to large numbers of transient humidity faults.
KEMA’s assessment has identified serious problems in the preparation for and the handling
of the incident by OETC management. We believe it is fair to say that the impact of the incident
could have been limited to a significant extent if proper preparation was in place and a
more prompt and adequate response had followed. Our review reveals a significant scope
for improvement to be achieved in future in order to bring the quality of operations within
OETC to a level in line with what could reasonably be expected from a transmission operator
operating within the Oman electricity market.
Review Incident Shinas August 2007 20 09.10.2007
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