Retrofit for old MV switchgear

ABB is the first of the major switchgear suppliers in the UK to offer the supply and installation of an Energy Network Association (ENA) assessed retrofit service for out-dated and ageing medium voltage switchgear for Distribution Network Operators (DNOs). This offer now enables DNOs and other industrial network operators to address the increasing obsolescence, maintenance, reliability and safety issues associated with legacy oil-filled circuit breakers, which often date back as far as the 1950s.
Equipment safety rating

When Ofgem introduced a new health and safety index in 2010, it had the objective of rating network equipment and ensuring safe operation. The move prompted DNOs to review the condition of their plant and rate its condition from 5 (the lowest) to
1 (the highest).
While much of the original fixed switchboard equipment, such as housings and busbars, was found to be in good condition, the circuit breakers moving parts were showing their age, meaning the condition of many switchboards was ranked as ‘low’. The knock-on effect is that DNOs are keen to take action to raise safety standards.

ENA-assessed solution
ABB’s retrofitting service brings existing switchboard equipment up to modern safety and reliability standards. The service, offered in collaboration with ABB’s OEM partner P&B Switchgear, successfully completed assessment by the ENA as well as field trials with UK utility customers.
In most cases, retrofitting an ABB circuit breaker will boost a switchboard initially rated at 4 up to a level of 2 and will extend its life by 20 years or more.
Essentially, the field trials gave vital experience of the variations presented by existing switchboard equipment and helped to plan and manage the solution required to meet the challenges of the hundreds of possible permutations in substations across the country.

Cost and installation considerations
Retrofitting new circuit breakers costs around 30 per cent less than completely replacing the switchboard and there are significant reductions in outage time and project complexity.
It’s an approach that involves minimal disruption to normal substation operation and cabling can remain in situ, so there is no need for a total outage. Another benefit is that the upgrade can be treated as operational expenditure (OPEX) rather than capital expenditure (CAPEX).
The solution has been designed to fit the characteristics of the vast majority of equipment produced by UK manufacturers, including GEC, Reyrolle, South Wales Switchgear, Brush and many others.
Hundreds of retrofit and circuit protection permutations are available and they are based on two central options, which replace oil circuit breakers with a vacuum circuit breaker with either a spring-operated mechanism or with a magnetic actuator. The two main options for retrofitting circuit breakers are:
VOR-S (replacement with a vacuum circuit breaker with a spring operated mechanism) which is built around ABB’s well-proven Vmax vacuum circuit breaker.
VOR-M (replacement with a vacuum circuit breaker with a magnetic actuator mechanism) incorporating P&B Switchgear and ABB components.

Sixty circuit breakers for SSE
In a major fast-track contract with SSE, eight substations on Scotland’s east coast were retrofitted with 60 new circuit breakers.
During the project, 60 South Wales Electric C4X and C8X circuit breakers were replaced with retrofit units based on ABB’s well-proven Vmax vacuum circuit breaker. The circuit breakers were also upgraded from 400 A and 800 A to 630 A and 1,250 A
respectively.

Switchgear retrofit for UK Power Networks’ London substations
Recently, ABB won a four-year framework agreement with UK Power Networks to provide a retrofit service for medium voltage switchgear installed at London distribution substations. The programme covers legacy class QA/QF oil-filled circuit breakers, which are now unsupported by their original manufacturer.
For UK Power Networks, there are two key drivers for the retrofit approach. First, the substations play a critical role in meeting London’s ever-growing demand for electrical power. This means that outages must be kept as short as possible and planned a long time ahead, so there are important operational reasons for upgrading rather than installing new equipment. Second, space is at a premium, which also makes the construction of new substations challenging.
Installing a new state-of-the-art circuit breaker will bring the switchgear panels up to modern safety and reliability standards while offering a life extension of 20 years or more. Network downtime is also reduced as site disruption is minimised and there is no need to disturb or replace cabling.
The replacement circuit breaker design deployed for UK Power Networks is based on the type-tested Energy Networks Association assessed design developed by P&B Switchgear. It has required some modification to be compatible with the unique shuttering mechanism. To assist with the final design and test phases, including partial discharge testing, UK Power Networks has made obsolete housings available.
The ABB retrofit philosophy will help UK Power Networks meet Ofgem’s RIIO (Revenue = Incentives + Innovation + Outputs) model, which encourages network operators to invest efficiently for continued safe and reliable services and innovate to reduce network costs. Under the model, Ofgem is rewarding operators for investing efficiently and extending the life of existing assets.
The first project within the UK Power Networks framework is for a 28-panel board, around 40 m wide and more than 2.5 m high. It represents a good example of the advantages of retrofitting, since the exercise will be completed within a one-week outage. Replacing this very large board with new equipment would have required a major logistical and civil engineering project, both to remove the old switchboard and to install the new one, involving building modifications, new foundations and cabling work.

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