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For decades, pole mounted reclosers have been applied in substation environments as circuit breakers. Reclosers offer extensive functionality applicable to this environment, and usually offer a cost saving against traditional circuit breaker and instrumentation arrangements.
In this article, we cover the rationale for Recloser application to substations, the limitations, some options and accessories to improve the electrical design, and finally some general tips when considering this application.
Why use Reclosers in Substations?
There is one main reason – Cost saving through integration.
Reclosers are circuit breakers with the added requirement for a short duty cycle. They are a circuit breaker with the ability to open and close quickly.
In the substation context, the reclose function is less commonly used, but the product is also a circuit breaker, and there are other advantages to using Reclosers.
Integration:
Recloser products, such as the OSM Recloser, are supplied complete with a control system that includes the protection relays, SCADA RTU and automation capabilities.
Traditional substation equipment requires separate procurement of relays, communications and the primary circuit breakers.
This integration can offer significant cost savings, not only in upfront capital expenditure, but also in reducing the commissioning cost. When the product is factory tested as a full system, onsite commissioning is greatly reduced.
When using an integrated Recloser system such as the OSM Recloser, there is no need to run separate communications between relays and breakers or conduct point-to-point tests on this wiring. Instead, engineers and technicians can largely rely on the works practices developed for the pole mounted recloser installations.
What are the limitations?
The primary limitation with Recloser application in substations is fault current and load current rating. Recloser specifications generally reach 16 kA peak interrupt capacity and 38 kV. This limits their application to smaller substations, such as rural substations and renewable integration sites. These sites tend to have lower fault currents. However, this specification is the only limit. Reclosers have been used in large urban substations, provided fault currents remain within the limits of the equipment capacity.
What added options and accessories are useful?
Substation Mounting Frame
In brownfield or retrofit sites, Reclosers can often be mounted on the old mounting frames of retired switchgear. However, when a new mounting arrangement is needed, the substation mounting frame is an ideal option.
NOJA Power have developed a steel mounting arrangement to install an OSM Recloser in a substation environment. This steel pole can be bolted to a concrete slab, providing a stable mounting arrangement for the OSM Recloser and RC Control.
