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

0BInvestment Evaluation Summary
TNM-GS-809-0720
The YTS relay was installed in 2007. Issues associated this type of relay are discussed above. The Siemens 7SD511 is a
microprocessor based relay that utilises digital differential communications and was installed in 1997. This type of relay
has nine recorded defects over the past five years and there are currently 38 relays installed throughout the transmission
network.
The Siemens 7SD511 is a microprocessor based relay that utilises digital differential communications and was installed
in 1997. This type of relay has 9 recorded defects over the past 5 years and there are currently 38 installed around the
state with 8 spares that have been used in previous installations. These relays will be retained as spares.
Chapel Street–Creek Road–Risdon 110 kV transmission line protection scheme
The transmission line protection on the Chapel Street–Creek Road–Risdon 110 kV transmission line comprises a GEC
type YTS static distance protection relay and an Areva P543 microprocessor relay.
The YTS relay was installed in 2007. Issues associated this type of relay are discussed above. The Areva P543 relay was
temporarily installed in 2006 as part of a transmission line configuration and augmentation project. This relay will be reinstalled
elsewhere in the transmission network or retained as spares.
110 kV bus bar protection
The 110kV bus bar protection installed at Creek Road Substation is a GEC MBCZ low impedance scheme of a static
design that was installed in 1996. This type of scheme has 17 recorded failures over the past five years and there are
currently nine schemes of this type installed throughout the transmission network. Spares are no longer available for this
type of bus bar protection. This type of bus bar protection is not suitable for the revised bus bar configuration and as such
will be retained for spare parts.
4.10 NETWORK DEVELOPMENT CONSIDERATIONS
The 110 kV switchyard at Creek Road Substation is configured as a ring bus arrangement. This arrangement presents
reliability and operational issues, including:
� all transmission circuits and loads are connected to single points on the 110 kV bus bar;
� reduced operational flexibility. Removal of critical plant from service for maintenance purposes requires extensive
planning and transmission network reconfiguration. Loads cannot be transferred to different points on the bus bar,
which constrains plant outages times to summer months (as plant not being maintained is also required to be out of
service). and
� the ring bus arrangement does not readily facilitate extension for future development projects.
Redevelopment of Creek Road Substation 110 kV will enable reconfiguration of the switchyard arrangement to provide
improved reliability and operational flexibility. Each transmission circuit and load will have the ability to connect to
multiple points on the 110 kV bus bar, which will enable all major items of plant to be maintained with minimal
reduction in security of electricity supply.
In 2006, the 110 kV transmission lines between Chapel Street and Risdon substations were augmented to provide
additional capacity to southern Tasmania. The 110 kV transmission network at Creek Road Substation was reconfigured
by removing one 110 kV transmission line connection (and creating a normally-open teed arrangement) to Creek Road
Substation to avoid the need to augment the 110 kV bus bars at Creek Road Substation. This reconfiguration reduced the
security of electricity supply to Creek Substation, albeit whilst providing other benefits. The redevelopment of Creek
Road Substation 110 kV provides the opportunity to install 110 kV bus bars of adequate capacity to optimally configure
the 110 kV transmission network in the vicinity of Creek Road Substation, thereby improving the security of electricity
supply to Creek Road Substation.
5 CUSTOMER CONSULTATION
Transend intends to liaise directly with relevant stakeholders regarding the intent, scope and implementation of the
project. The proposed redevelopment project has been highlighted on a number of occasions during Transend’s Annual
Planning Review process.
© Transend Networks Pty Ltd 9 of 17