Understanding the Auckland electricity network

Transcription

1 Understanding the Auckland electricity network

2 Introduction This presentation describes how electricity reaches homes and businesses in Auckland, with a particular focus on the distribution network run by Vector. Vector is responsible for delivering electricity to 544,513 Aucklanders on behalf of electricity retailers. Vector s network supplies customers from Wellsford in the north, to parts of Papakura in the south. Vector s network is comprised on 18,093 kilometres of overhead lines and underground cables.

3 How electricity reaches Vector s network Sub transmission network Transmission network Power stations Electricity is generated at power stations e.g. Benmore hydro-power. network Electricity is transported from power stations around the country via s transmission network the National Grid to local electricity distribution networks (like Vector). Local electricity distribution networks connect to s transmission network at Grid Exit Points (GXPs). GXPs are large s where the power voltage is reduced from 220kV/110kV transmission voltages for supply into local distribution networks. Grid Exit Points (GXP) (14 in Auckland) Vector network From GXPs power flows into Vector s 110kV/33kV/22kV sub-transmission network and is transported to Vector zone s. High Voltage (HV) network s (107 in Auckland) At zone s, the voltage is further reduced and electricity transported via the High Voltage (HV) network to distribution s. Low Voltage (LV) network s (23,602 in Auckland) s reduce the voltage again and feed electricity into the Low Voltage (LV) network which supplies power directly to customers. NOTE: Some commercial and industrial customers require power at higher voltages and are supplied directly from Vector s sub-transmission or High Voltage (HV) network. (544,513 in Auckland) Vector is responsible for delivering power to 544,513 customers in Auckland from Wellsford in the north to parts of Papakura in the south via its 18,093km network of overhead lines and underground cables.

4 How electricity flows through Vector s Auckland network From Grid Exit Points (GXPs) electricity flows into Vector s sub-transmission network and is transported to zone s. Power stations The voltage is reduced at zone s and supplied to distribution s. From here the voltage is reduced again and supplied into the Low Voltage (LV) lines network which provides power directly to customers. network Grid Exit Point (GXP) Grid Exit Point (GXP) possible possible possible Vector s network design enables use of backfeeding to temporarily restore power supply to customers by supplying power from adjacent areas. This can only be achieved if the power supply allows i.e. demand for power in the area is less than available supply. In some cases, Vector will temporarily switch off customers hot water cylinders to free up electricity for backfeeding. The following slides explain how backfeeding is used.

5 Loss of supply at a GXP Partial loss of power supply at a GXP will not affect the power supply out of the GXP. However, total power loss at a GXP such as through de-energisation will. This causes loss of power to the Vector zone s the GXP supplies, and subsequently to the network that feeds customers from the affected zone s. Power stations network Grid Exit Point (GXP) possible Vector can reconfigure its network to backfeed and liven parts of the affected network. Grid Exit Point (GXP) possible possible

6 Loss of supply at a Vector zone If power supply is lost at one of Vector s zone s, Vector can reconfigure its network to enable backfeeding to liven parts of the affected network. Power stations network Grid Exit Point (GXP) Grid Exit Point (GXP) possible possible active

7 Loss of supply at a Vector distribution If there is a power failure at a Vector distribution the outage will be localised and only affects the customers supplied from the distribution. Power stations is not possible at this localised level (between the distribution and the customers) because there is only a single feed to the customers. network Grid Exit Point (GXP) Grid Exit Point (GXP) possible possible possible

8 Understanding the development of the Penrose GXP

9 How the Penrose GXP has developed The Penrose Grid Exit Point (GXP) was built in the early 1920 s. Building and development around the Penrose GXP from the 1940s onwards, including construction of the Southern motorway bordering the site, has constrained the site from expanding. It has also limited exit routes for Vector s sub-transmission cables. Significant load growth (demand for electricity) in the surrounding areas, and development in the site to meet this demand has added further site constraints. The is built on hard basalt rock which makes alternative corridors difficult to construct.

10 The Penrose GXP The Penrose Grid Exit Point (GXP) is the largest of the 14 connections between s transmission grid and Vector s network. CBD tunnel portal Penrose has two separate switchyards (110kV and 220kV). 33kV switchgear Cables feed: Glen Innes, Newmarket (part), The Drive 110kV switchyard 220kV switchyard Cables feed: Mt Wellington, Westfield (part), Carbine, Sylvia park, McNab (part) CBD 33kV switchyard Cables feed: Remuera, Newmarket (part), St Johns, Orakei, St Heliers Cables feed: McNab (part), Onehunga, Te Papapa, Westfield (part), Rockfield Vector cable corridor in the residential suburbs in the Eastern Bays, Remuera and Epsom, the commercial/retail suburb of Newmarket, and the industrial area through Penrose, Westfield and Mt Wellington are supplied from equipment in the 220 kv switchyard. in the Auckland CBD and neighbouring suburbs are supplied from the 110 kv switchyard via cables installed in Vector s CBD tunnel. There are multiple corridors for Vector s supply cables to exit the Penrose.

11 The Penrose GXP supply area St Heliers Orakei Newmarket Glen Innes Remuera The Drive Penrose GXP St Johns Mt Wellington Rockfield McNab Sylvia Park Onehunga Te Papapa Carbine Westfield GXP Vector zone Vector s sub-transmission cables from s Penrose GXP supply power to 15 Vector zone s in Eastern Auckland, servicing 75,339 customers.

12 Understanding what happened at the Penrose GXP on 4 October 2014

13 Saturday 4 October Electrical fault causes fire at Penrose GXP Saturday 11:21pm An electrical fault in a transition joint in the cable trench at the Penrose GXP caused a fire to start. CBD tunnel portal 33kV switchgear Sunday 2:04am Cables feed: Glen Innes, Newmarket (part), The Drive s remote control system recorded a series of unusual alarms. 110kV switchyard 220kV switchyard Cables feed: Remuera, Newmarket (part), St Johns, Orakei, St Heliers Sunday 2:11am The fire causes cables to start tripping from 2.11am which begins interrupting the power supply to customers. Sunday 2:17am Cables feed: Mt Wellington, Westfield (part), Carbine, Sylvia park, McNab (part) CBD 33kV switchyard Cables feed: McNab (part), Onehunga, Te Papapa, Westfield (part), Rockfield Fire Vector cable corridor A member of the public calls the Fire Service.

14 Sunday 5 October 2:26am-3:32am Getting control of the fire Sunday 2:26am The Fire Service arrive on site. Sunday 3:06am begins de-energising a large proportion of the Penrose GXP to allow safe access for the NZ Fire Service. St Heliers Orakei Newmarket Sunday 3:17am Glen Innes Remuera The Drive Penrose GXP Power supply to 15 Vector zone s is lost as a result of the de-energisation and subsequently 75,339 customers lose power. St Johns Sunday 3:22am The NZ Fire Service enters the switchyard. No site access for Vector or crews until the fire is extinguished. Mt Wellington Rockfield McNab Sunday 3:32am Sylvia Park Onehunga Fire fighting begins and NZ Fire Service start applying foam. Te Papapa Carbine Westfield Power outage Partially restored Power restored

15 Sunday 5 October 9:17am Vector control room begins power restoration via backfeeding Sunday 9:17am Vector s control room restores most of Onehunga and parts of Newmarket using backfeeding. continues with restoration work throughout the day, testing and slowly relivening GXP equipment. St Heliers Orakei Newmarket Sunday 9:57am Glen Innes Remuera The NZ Fire Service hand the site back to and begins inspections and preparing the site for relivening. St Johns Sunday 3:00pm onwards The Drive Penrose GXP partially relivens GXP and Vector is then able to begin the process of relivening its undamaged cables. Mt Wellington Rockfield McNab Power supply is partially restored at s Penrose GXP. Sylvia Park Onehunga Te Papapa Carbine Westfield Power outage Partially restored Power restored

16 Sunday 5 October 6:21pm Relivening the undamaged cables Sunday 6:21pm Vector restores power to seven Vector zone s which are fed from undamaged cables. Nearly half the 75,339 affected customers have their power supply restored. St Heliers Orakei Newmarket Throughout Sunday night, Vector s control room carries out extensive reconfiguration to backfeed supply into affected areas, restoring power to an additional 18,786 customers in St Heliers, Remuera and Mt Wellington. Glen Innes Remuera The Drive Penrose GXP St Johns Mt Wellington Rockfield McNab Sylvia Park Onehunga Te Papapa Carbine Westfield Power outage Partially restored Power restored

17 Monday 6 October 9:06am Restoration work gets underway Monday 9:06am Vector s control room undertakes hot water load controlling in some areas to reduce electrical load to enable additional backfeeding to the affected area. St Heliers Orakei Newmarket A mobile crane arrived onsite to lift cable drums into the yard. Cables were then pulled through the yard along the routes agreed between and Vector and jointing of cables commences. Glen Innes Remuera The Drive Penrose GXP St Johns Mt Wellington Rockfield McNab Repairs to the first two cables are completed early Tuesday morning. Sylvia Park Onehunga Te Papapa Carbine Westfield Crews work continuously to complete repairs. Working conditions over the initial 24 hours of the repair operation were challenging, with periods of severe rain, high wind and hail during Monday night. Power outage Partially restored Power restored

18 Tuesday 7 October 7:41am Restoration work nears completion Tuesday 7:41am Vector continues with cable repair work and re-energisation, restoring additional customers. St Heliers At 7.41am 2,047 customers remain without power. (2.7% of the originally affected customers). Orakei Newmarket Glen Innes Remuera The Drive Penrose GXP St Johns Mt Wellington Rockfield McNab Sylvia Park Onehunga Te Papapa Carbine Westfield Power outage Partially restored Power restored

19 Tuesday 7 October 2:08pm Restoration complete Tuesday 2:08pm Power is restored to all 75,339 affected customers. St Heliers Orakei Newmarket Glen Innes Remuera The Drive Penrose GXP St Johns Mt Wellington Rockfield McNab Sylvia Park Onehunga Te Papapa Carbine Westfield Power outage Partially restored Power restored

20 Vector s response to Penrose outage Vector regrets the disruption to customers during the outage in October Everything was done to ensure the network was repaired as quickly as possible, however, we do understand and acknowledge the impact the outage had on homes and businesses. Immediately after power was restored, and Vector embarked on a thorough investigation including appointing independent international experts to identify the cause, extent and impact of the Penrose fire and subsequent electricity outage. Both parties have also worked collaboratively with the Electricity Authority (EA) to ensure it received the information required to conduct its own separate investigation, and welcomes the EA report on the incident. All incidents provide lessons and the only mistake would be not learning from them. Throughout the internal and external investigations, and Vector s focus has been on identifying and resolving any issues as quickly and thoroughly as possible. The majority of recommendations identified in both the EA and joint and Vector reports have already been completed and progress is well advanced on the remainder. Vector wishes to acknowledge the disruption caused by the Penrose outage by making a Vector service level payment to affected customers. This is a voluntary payment Vector makes available to customers if an outage occurs and power is not restored within Vector s published service levels. This will be available to claim from 2 December.

21 The investigation key learnings While the independent cable expert has concluded that the cause of the fire was rare, we have taken valuable learnings from the incident. We are now focused on finalising implementation of the recommendations to address these: Failures of cable joints installed in air can cause fires, and, if there are a number of cables in close proximity, the collateral damage can have a significant impact on customers; Risk management processes did not identify very low probability risks of events that had not previously occurred on the network; The nature of the incident identified some gaps in current operating practices; The current asset and risk management processes at the physical interface between Vector and s networks must be improved.

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