PZM Solutions — Lowering High Reg Ops

PZM has created Alerts in our software to provide utilities information they can act on to improve their system. PZM Solutions are ideas we have that utilities can use to respond to alerts and make meaningful improvements to their system.

Feedback control theory illustrates you can't control anything without feedback and response. Management guru Peter Drucker says what gets measured, gets managed. PZM uses your inspections to provide the important feedback and measurements needed to control and manage your system. PZM Solutions are ideas for a response. Using this process, you will be able to stay in control of your operation.

PZM Reg Ops Alert

PZM Reg Ops Alert feature measures how many times your regulator changes taps and calculates a monthly and annual average based on the number of operations between inspections.

A high regulator ops score indicates a regulator that could be operating too much.

Why should a utility reduce regulator operations:

• Reducing operations extends the maintenance intervals of voltage regulators.
• Reducing operations will extend the life cycle of voltage regulators.

Voltage Regulator Operation

The following three settings are what a voltage regulator controller uses to control voltage:

Voltage Setpoint

This sets the desired voltage at the output of the regulator. It is set on a 120V basis. Generally, the output is set higher than 120V to account for voltage drop downstream, with the goal of delivering 114V to 126V at all loads, or from 95% to 105% of the 120V basis. A setpoint programmed at 123V would deliver a 102.5% voltage output.

Voltage Bandwidth

Voltage regulators make voltage changes in steps. Typically, each step moves the voltage by 0.625%. Because of these step increases and step decreases, it is important to program an acceptable range of voltage for the regulator to operate. This acceptable range is called the voltage band. The voltage band is also programmed on a 120V basis. The bandwidth setting is the total range, and half the range will be below the setpoint, and half will be above the setpoint. With the voltage setpoint programmed at 123V and the bandwidth programmed at 2V, the acceptable voltage range would be from 122V to 124V or 101.67% to 103.3%. If the regulator output voltage is operating in this acceptable range, it is considered 'in band,' and if the output voltage is outside of this range, it is considered 'out of band.' A bandwidth programmed between 1 and 3 volts is typical.

Time Delay

Voltage regulators should always be programmed with a time delay before responding to an 'out of band' voltage level. This time delay will ensure the voltage regulator doesn't overreact to a voltage is out of band for a short duration. Changing voltage requires a tap changer operation and causes some contact wear, so it is best not to have a regulator operate if it is a quick voltage swing.

For example, if a large motor starts on a distribution feeder, the inrush current might cause the voltage to dip momentarily and recover. Raising the voltage will not affect the motor start-up, so it is best not to operate and cause undue wear to the regulator. A time delay programmed between 20-60 seconds is typical. Time delay with cascading regulators is an important consideration when programming time delay. Rural feeders are typically several miles long and may require several regulators to maintain acceptable voltage along the line's entire length. These are called cascading regulators (See figure below).

Voltage regulator time delay must be coordinated when there are cascading voltage regulators. The time delay should increase as the distance from the source increases. This allows the first regulator a chance to correct the voltage first. Typically the time delay between cascading regulators should be at least 15 seconds.

PZM Solution — Reducing Regulator Operations

There are two main strategies to lower voltage regulator operations, increasing the bandwidth, and increasing the time delay.

Increase the Bandwidth

Programming a larger bandwidth increases the acceptable range of voltage at the output of the regulator. This will keep the regulator 'in band' longer. By staying in band longer, the voltage regulator will operate less often. When increasing the bandwidth, ensure the upper band doesn't allow a voltage out of compliance with your utility standards (typically 126V or 105%). The upper band is the setpoint + ½ the bandwidth.

Extend Time Delay Setting

Programming a longer time delay will reduce the operations on a voltage regulator. The time delay clock begins when the voltage crosses the band edge and remains 'out of band.' If the voltage remains 'out of band' for the programmed time delay, the voltage regulator will operate until it brings the voltage back 'in band'. When adjusting the time delay on a rural feeder with cascading regulators, be sure to maintain time delay coordination.

Additional Ideas to Lower Operations on Voltage Regulators

PZM Solution Idea — Add capacitor banks

Adding capacitor banks can be used to reduce inductive VAR flow and improve the voltage on a feeder. This voltage improvement can reduce voltage regulator operation.

PZM Solution Idea — Reduce or Balance Loads

The idea behind reducing or balancing loads on a feeder is to lower the current flow, decrease the voltage drop, and improve the feeder's voltage. This voltage improvement can reduce voltage regulator operation. Reducing load is not always possible if no tie point exists to relieve the load on a feeder. A capital project may be required to build a new feeder to handle some of the load.

Additional Reading

• Understanding PZM Alerts

Transformer Alerts

Voltage Regulator Alerts

DC Control System Alerts

Protection Device Alerts