New utility facilities must be tested before going live to verify proper operations of relays and power protection. Operators can test their new facilities in one of two ways: use the existing power grid or deploy load banks. Using the power grid to commission your utility facility can lead to many issues, including an inability to precisely control critical voltage, current and load parameters. You also have little control over scheduling a power grid test.
When you use load banks instead of the power grid for utility commissioning, you can help speed-up the commissioning process, improve testing accuracy, allow greater scheduling control and create an opportunity for lowering overall commissioning costs.
According to utility operators, here are some reasons they use load banks for commissioning:
- Utilities can get a specific amount of MW load to in-service all protective relays in the station. Many times, not enough load exists in certain areas to polarize the protective relay current circuits. Having a dedicated amount of MW load allows the CT secondary current circuit in the protective relay scheme to have the MFG recommended minimum current.
- Often the test equipment utilities use to measure the current circuits in the protective relays, such as phase angle meters made by Megger, Arbiter or Dranetz, requires a minimum amount of current per the MFG specs. Load banks help them get the minimum amount of secondary current -- 50 milliamps by loading up the primary.
- Because of no inductive or capacitive factors, resistive load banks provide 100% resistive load and simplify in-servicing the equipment (phase angle comparison).
- With load banks, no customer load is used – just the load banks. So, if issues surface, testing with load banks mitigates customer outages.
- Relying on operations and lineman switching to get the required amount of load for testing can lead to expensive project delays. Load banks eliminate this dependence. Utilities just hook up the load bank at the substation and are ready to test. In these situations, renting load banks can sometimes produce savings of 25 to 50%.
- If a utility has a tight schedule and doesn’t want to risk a project delay, they will use load banks for testing. The utility connects a load bank at the station and can in-service ALL lines, even future lines, during one testing schedule. As future lines are added, grid ops and the lineman just bring in the cable and operations can energize the circuit with minimal testing.
- Utilities often use contractors to perform the in-service and testing. Experienced contractors are aware of the minimum current requirements of the phase angle meters. Therefore, they use load banks to increase the current flow on the power lines to get proper secondary current.
Comrent provides solutions for utility testing and commissioning. We provide load bank rentals and service, cables, switchgear, transformers, power quality meters and more. For a complimentary consultation, contact us today at 888-881-7118 or visit our website for more information.
Originally published by Steve Tao via LinkedIn