Reactive power compensation and frequency converter interference protection
Most electrical network consumption devices require reactive power in addition to active power to operate. Such devices include motors, discharge lamps, and transformers.
Reactive power compensation
Most electrical network consumption devices require reactive power (Q) in addition to active power (P) to operate. Such devices include motors, discharge lamps, and transformers. The reactive power required by these devices can either be drawn from the electrical network or generated near the devices using compensation equipment.
Transferring reactive power through the electrical network increases voltage, power, and energy losses in cables and transformers and reduces the capacity for transferring active power.
In the price list, part of the reactive power is free of charge. For the excess amount, Caruna charges a power fee according to the price list. The reactive power fee is charged for reactive power taken from and supplied to the network.
It is recommended to reserve space withinthe main switchboard for reactive power compensation, meters, current transformers, and control units when the main fuse size exceeds 63 A. Compensation must be installed at each usage point after metering.
Reactive power compensation should be distributed in the most suitable way among electricity generation, transmission, and load points. Compensation devices that are permanently connected to the network or controlled by a timer are generally not allowed.
Caruna must be informed in advance or on the day of maintenance about any maintenance of compensation devices or other exceptional situations related to their use, such as equipment failure, so that reactive power spikes caused by maintenance can be taken into account.
Guidelines for implementing compensation
Street and road lighting using discharge lamps must always be implemented with compensated luminaires or another approved method, regardless of fuse size.
In individual and group compensation, the compensation must not exceed the reactive power requirement of the device or device group.
For automatic compensation systems:
- The planning must be carried out by a qualified electrical designer. It is recommended to also check for possible harmonic distortions so they can be eliminated using a harmonic filter installed in the compensation equipment.
- Current transformers for reactive power control must not be related to billing measurements and must comply with SFS 2874 recommendations for measuring transformers.
Frequency converter interference protection
When designing and installing frequency converters, the manufacturer’s instructions and limitations must be followed.
Frequency converters connected to the distribution network must comply with IEC/EN 61000-3-12 and IEC/EN 61800-3 (C1 or C2) standards. The switching frequencies of the devices must be programmed within the range where these standards are met.
Motor cables must be EMS-shielded, comply with the manufacturer’s specified maximum cable lengths, and be grounded 360 degrees at both ends. The cable must run uninterrupted and separately from other cables from the frequency converter to the motor. It is recommended to install efficient external network filters on the supply cables of frequency converters to prevent interference with remotely read electricity meters.