The 110 kV bus rationalisation and local backup protection upgrade project was the third of three significant works activities to be undertaken by Transpower in the redevelopment of Timaru Substation. This final project is required to rationalise the 110 kV busbar. The principle aim of this project was to remove the top bus, uprate the lower bus to achieve a 1,200 Amp rating and install two new DCB type bus coupler CBs. Works also involved installing 110 kV Busbar / CB Fail protection as well as completing local back up protection upgrades on each of the four connected transmission circuits to improve security of supply and the protection of the power system.
The Scope of Works
1.1 110/11kV Switchyard and Primary Works
The switchyard design included the following installations:
- Replace the central 110 kV switchyard cable duct and a 17m length of in the vicinity of bay 40.
- Resurface the 110 kV switchyard on completion of 110 kV switchyard primary works.
- Removal of the existing top Bus A including disconnectors (DIS43, 47, 53, 63, 67, 73, 83, 87, 93, 107, 113, 123, 127 and 133).
- Removal of DIS57, DIS117, DIS137 & CB138 from existing bottom Bus B
- Uprating of the longitudinal and transvers busbars and existing disconnectors DIS77 & DIS97 to meet the new bus rating, 1200A
- Splitting of the 110 kV Bottom Bus into three sections.
- Installation of new 110 kV junction boxes JB62, JB78, JB82, JB98, JB122 & JB132. Removal of existing JB’s ‘A’, ‘B’, ‘C’, ‘D’, ‘E’ & ‘F’ and SCADA JBs 1 & 2.
- A temporary Tekapo A circuit 1 bypass arrangement and protection scheme was required for the temporary bypass of CB132.
- A temporary T3 bypass arrangement was required during the outage of 110 kV Bus B.
1.2 Protection, Control and Metering:
- A high impedance busbar / CB Fail protection scheme comprising three discriminating zones and an overall check zone. The new bus zone scheme included two new bus couplers; CB78 & CB98.
- Transmission circuit protection for each of the four connected circuits (CB62; TMK1, CB82; STU, CB122; TMK2 & CB132; TKA) shall be upgraded to Transpower’s duplicate Dist/DEF1; SEL421 and Dist/DEF2 Siemens 7SA522 protection relays.
- CB72; Tekapo A CB132 bypass circuit Dist/DEF1 SEL421 protection relay shall be installed to provide temporary protection for the TKA circuit.
- Two 110 kV bus couplers CB78 and CB98 had new OC(CBFail); SEL451 protection
- Modifications/additions were made to the existing 110kV voltage selection, associated control/mimic panels and secondary systems to accommodate the 110kV Bus Rationalisation
- New ResV(DefT); P922 relays were installed into existing 110/11 kV supply transformer T3 & T6 protection panels.Modifications were made to each of T3, T4 & T6 to interface to the new 110 kV Busbar / CB Fail protection (hardwired) and 11 kV load shedding schemes (GOOSE messaging).
The project team included Andre Manton as project Manager, Nico Bosman as lead technician, Tim Scherer as project supervisor and a number of skilled electrical fitters and lines staff to complete this project safely, on time and with in budget.