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

5. CUSTOMER CONSULTATION
0BInvestment Evaluation Summary
TNM-GS-809-0720
Transend has liaised with all relevant stakeholders regarding the planned works at Farrell Substation. Short outages will
be required for each of the transmission line, transformer, and bus coupler circuits to implement the works. Some of
these outages will constrain generation, so it is important that planned outages be coordinated with Hydro Tasmania to
ensure that the impact of the planned outages is minimised.
6. BENEFITS
Replacement of the 220 kV and 110 kV bus bar protection schemes at Farrell Substation will provide the following
benefits:
� the likelihood of unplanned bus bar protection scheme outages will be reduced, thereby improving the reliability
and security of the transmission network;
� the occurrence of events that cause power flows through the substation to be constrained will be reduced;
� obsolete, unreliable and difficult to maintain protection schemes will be replaced with modern, reliable
equipment that incorporate self supervision functions, thereby reducing ongoing operations and maintenance
costs; and
� ensure ongoing compliance with the NER;
� facilitate future capital works at Farrell Substation;
� additional disturbance recording facilities will be provided, thereby improving power system analysis and fault
response capability.
� reduction in the risk of non-operation of the bus bar protection scheme for bus bar faults. If faults are not
cleared appropriately then bus bar faults can result in damage to primary equipment, system instability issues
and forced outages; and
� reduction in the risk of mal-operation of the bus bar protection schemes due to partial failure of the scheme.
Mal-operation of the scheme (ie operation of the scheme when there is no fault present) can result in forced
outages and instability issues.
7. OPTIONS ANALYSIS
The following viable options have been considered to address the identified investment needs and compliance issues
associated with the bus bar protection schemes at Farrell Substation:
1. maintain the existing bus bar protection schemes and defer replacement;
2. replace the 110 kV and 220 kV bus bar protection schemes at Farrell Substation without installing duplicate
systems; and
3. replace the 110 kV and 220 kV bus bar protection schemes at Farrell Substation and install duplicate systems.
An alternative option that included maintaining the existing bus bar protection schemes and installing additional schemes
was considered but discounted because it did not provide any material benefits. The existing bus bar protection schemes
would still be susceptible to failure and would not be able to be repaired because spare components are not available.
The viable options are discussed in further detail in the following sections.
7.1- MAINTAIN THE EXISTING BUS BAR PROTECTION SCHEMES AND DEFER
REPLACEMENTS
This option comprises maintaining the existing Brown Boveri type INX2 bus bar protection schemes.
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