Leader / Follower Scheme for Single Phase Step Voltage Regulators

Leader / Follower

This is a scheme to keep regulators on the same tap position.

A feed-back loop is required between Leader and Followers to ensure locked step.

Regulates voltage based on the Master device.

It is a firmware enhancement, which is now supplied pre-loaded in controls, but may require additional communication loop*

Compatible CL-6A, CL-6B and CL-7 Controls.

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*   For CL-6A, CL-6B and Single-phase CL-7 a communication loop is required to enable communication between regulators.  CL-7 Multi-phase control does all signal processing within the one control so no additional communication hardware required for Leader/Follower and only one communication interface required for SCADA for all regulators in the set.

Leader/follower applications

The regulator control panel traditionally operates in an autonomous mode with each individual control making decisions with regard to the proper operation of the connected apparatus for Single-phase Regulation of Utility Voltage Distribution systems.  The Leader/Follower feature allows devices in an operating group to act together when making adjustments to apparatus output voltage.  Operating groups would be one of two defined system configurations.

Three-phase ganged operation

On a given distribution feeder, on a three phase output, utilities may gang two (Open Delta) or three (Closed Delta) apparatus together.   In this configuration utilities would require all apparatus to stay in step to provide “balancing” of the output voltage. Apparatus would be of similar design and specification and will be in close proximity to each other, typically in the same substation or on the same platform.  This configuration has found favour with New Zealand customers using Ground Fault Neutralisers (GFNs).

Paralleling operation

For the purpose of handling a larger capacity of load, or for providing a backup to a high priority load, the Leader/Follower feature can be used to parallel two banks of voltage regulators with a set of power transformers.   In this application, two voltage regulators located on each phase are paralleled by tying their common outputs together (i.e. Load “L” bushing to “L” bushing) thereby increasing their load output capacity, effectively regulating the voltage of a bus or feeder.   It is necessary for the transformers and the voltage regulator apparatus of the two banks to be of similar design and specification. The Leader/Follower feature maintains Locked-Step operation to eliminate the possibility of high reactive circulating current within the loop due to a voltage imbalance.

For more information:

MN225023EN       Leader/Follower Scheme Installation and Operation Guide.

Information on these products is available at:  



Power Contact

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Control System Contact

Stephen Dorrington

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