Transend - Appendix 5 Renewal capital expenditure - Australian ...

0BInvestment Evaluation Summary
TNM-GS-809-0720
2. Commission the new 220 kV Bus Zone Protection B scheme (GE Multilin type B90), maintaining the existing
Brown Boveri type INX2 scheme, de-commissioning the back up high impedance scheme in order to be able to
provide CT for new scheme.
3. Commission the new 110 kV Bus Zone Protection A Scheme (Areva P740), de-commission the
existing Brown Boveri type INX2 scheme.
4. Commission the new 220 kV Bus Zone Protection A Scheme (Areva P740), de-commission the existing Brown
Boveri type INX2 scheme.
3 INVESTMENT NEED
3.1 RELIABILITY
Each of the bus bar protection schemes at Farrell Substation (110 kV and 220 kV) has recently suffered failures due to
deteriorating components. A summary of the bus bar protection scheme failures at Farrell Substation is presented in
Figure 1 and Error! Reference source not found.. These failures have resulted in extended protection scheme outages.
The existing bus bar protection schemes have an auto-test function that operates once per week. If the equipment fails its
auto-test then the protection scheme is blocked from operation. Given the auto-test only operates once per week, then the
average protection scheme outage would be 3.5 days. An allowance of around 20 hours for repair then the total (average)
protection scheme outage time would be approximately be 4.5 days.
The failure rates for the bus bar protection schemes at Farrell Substation are increasing as the condition of the
components continue to deteriorate. The components of these systems fail randomly and they can not be predicted.
Figure 1 and Table 1 shows that as a whole the protection schemes are failing more often and are becoming more
unreliable over time.
Figure 1 – Bus bar protection scheme failures at Farrell Substation
Failures
3
2
1
0
1985 1990 1995 2000 2005 2010
Year
Table 1 – Bus bar protection scheme failures at Farrell Substation
Date Scheme
Outage duration of
Protection scheme
(estimated average)
Description of Failure
30/9/2008 110 kV 4.5 days 110 kV bus bar protection scheme failed autotest.
Output reed relays on modules MCT425A
and BLR429 replaced.
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