Power Facilities

What plant and substation distribution demands

Power facilities cover auxiliary supplies in generating plants, station service in substations and public distribution rooms of every kind. Such installations are part of the grid and its customer at the same time: a loss of supply directly affects the starting and stopping of main plant, the running of auxiliaries and the reliability of protection devices.

A distribution room carries many circuits with mixed duties — incoming, feeders, motor control and reactive-power compensation are often grouped in the same line-up. The equipment runs continuously and maintenance windows are short, so breaking capacity, short-time withstand and compartment separation matter more than in ordinary industrial distribution.

What power facilities have to cope with

The central tension is between continuous operation and the need to maintain: supply cannot simply be interrupted, yet a fault has to be isolated and cleared quickly.

• Many circuits with mixed duties: incoming, feeders, motor control and compensation grouped in one line-up
• High system short-circuit levels, demanding breaking capacity and short-time withstand from the assembly
• Short maintenance windows: a faulty unit must be replaceable without disturbing the rest of the line-up
• Limited cooling in the room, so temperature rise and ventilation have to be considered together
• Transformers energised continuously, making no-load loss a fixed item of consumption

An assembly for a power facility must not only fit the room — under fault conditions it has to confine the damage to a single compartment, a single withdrawable unit.

Coreda's approach for power facilities

We configure the LV assemblies separately for PC (power distribution centre) and MCC (motor control centre) duties, with wound-core oil-immersed transformers for station service and distribution.

Recommended configuration:

• S11, S13, S14, S20 and S22 wound-core oil-immersed transformers: three-phase triangular core geometry with no joints or air gaps, no-load loss 25–35% below a conventional stacked-core design, low noise and good short-circuit withstand.
• GGD LV switchgear: rated up to 3150 A, high breaking capacity and short-time withstand, standard degree of protection IP30 (selectable between IP20 and IP40), with ventilation slots top and bottom forming a natural convection path.
• MNS withdrawable LV switchgear: modular C-profile frame, busbar, functional-unit and cable compartments fully separated, mechanically interlocked drawers, usable as a power distribution centre (PC) or motor control centre (MCC).

Fixed cubicles take the incomer and the large feeders, withdrawable cubicles the branch and motor circuits; a faulty circuit is restored by fitting an identical spare drawer, which shortens the outage.