Electricity Asset Management Plan 2019-2029
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Vector Limited://
optimal and may result in poor performance of the arresters – we have initiated a project to investigate lightning arrestor earth banks and voltage coordination in general.
Strategy Earthing systems for zone substations are installed in accordance with Vector engineering standard ESE704 Zone Substation Earthing. Earthing systems for the distribution network are installed in accordance with Vector engineering standard ESE506 Distribution Earthing. Vector’s asset strategy for earthing systems is described in strategy report EAA600 Auxiliary Systems. Earthing systems are maintained and tested in accordance ESM603 Maintenance of Earthing Systems to ensure the integrity of earthing systems and its capability to carry fault currents and limit step and touch potentials. Zone substations and distribution earthing have a thorough testing regime that is performed every five years. LV pillar earthing is only to improve (lower) the overall MEN system resistance and is not installed to limit step and touch resistances and as such it is not tested but visually inspected as part of the maintenance regime. Assets are replaced when they reach their end of functional life, or pose a non-performance or health and safety risk, as detected during routine planned maintenance. Over more recent times Vector has switched to copper-bond steel earth rods and copper- clad steel conductor. Earth studies and measurements are undertaken for every new zone substation or BESS project to provide the necessary baseline information to design the new earthing system to ensure quick and efficient operation of protection systems and ensure safe step and touch potentials. 4.8 COMMUNICATIONS NETWORKS Vector operates an open communications architecture based on industry standards. The deployed technologies range from copper based buried cables to first generation optical fibre multiplex systems, to modern digital microwave systems and Ethernet based optical fibre networks. Vector’s communications network also consists of differing architectures and technologies, some of which are based on proprietary solutions. The physical network infrastructure consists of a mix of optical fibre, copper wire telephone type pilot cables and third party radio communication systems. In the Northern network, around 70% of the pilot cables used for operational communications are installed overhead and are prone to damage by the environment and lightning. The mostly copper pilot cables in the Auckland region are all installed underground. They are used for operational communication services and differential protection and alarms. Population and Age The copper pilot population is 50 plus years old. The pilot cable population in our dataset consists of many thousands of lines and it is not practical to compile age profiles or a key statistics table. Condition and Health Our Copper pilot cables have experienced some failures and their health is deteriorating. Fault finding on LV pilot cables is difficult, cumbersome and expensive. Strategy Copper pilot cables simply do not have the bandwidth to cope with the data communications requirements of the future energy network and our population is not in sufficient health to ensure reliability and resilience into the future. Hence, we have gradually been replacing Copper pilot cable with fibre optic cables and since 2006 we have been implementing an internet protocol (IP) based communications network. In light of the deterioration of the Copper pilot cables we are also systematically replacing subtransmission differential protection schemes with modern numerical protection schemes that use fibre optic communications channels (see the section above on protection relays). This replacement programme will continue for the first half of the AMP period. Not only will this improve the reliability of line differential protection schemes and SCADA but make provision for the expected increase in communications bandwidth as part of the Distributed Energy Resource Management System (DERMS). 4.8.1 PILOT CABLES Overview
4.8.2 RADIO LINKS Overview
Several digital microwave radio links were installed about 10 years ago to extend the IP operational WAN to zone substations in the Northern region. There are 295 overhead 11 kV network switches with SCADA remote control ability on
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