Operator Interfaces, Switches & Relays


Protection relays – control what you can

12 December 2022 Operator Interfaces, Switches & Relays


Nishan Baijnath.

The consequence of loadshedding on municipalities’ primary plants and substations have been discussed ad nauseum. The reality is municipalities are in survival mode, which is why realistic solutions should be provided to prevent equipment and unplanned outages.

With municipalities’ distribution centres and equipment taking immense strain due to load shedding, maintenance has unfortunately moved down the priority list. The time is now to implement what municipalities can control - protecting and monitoring installed equipment.

Protection relays play a fundamental role in the protection of both humans and machines. For example, a protection relay can prevent an incidence such as arc flash which has the potential to cause devastating damage to substations, and worse still, injury or loss of life.

However, not all options are equal; ideally a protection relay should be easy to install, require very little power to run, protect LV and MV distribution systems and control live distribution from a safe distance.

Why protection relays?

Protection relays are basically smart devices that receive inputs, compare it to a setpoint, and provide outputs. Inputs include current, voltage, resistance, or temperature while the main output of turning the power either off or on is incorporate with visual feedback in the form of indicator lights and/or alphanumeric display, communications, control warnings, and alarms.

In layman’s terms, a protection relay can detect abnormal conditions in the electrical system and automatically operate the circuit breaker to isolate this condition.

Importantly, once a protection relay detects a fault, it will operate automatically to activate the breaker’s trip circuit. The faulty circuit will therefore be disconnected from the system.

Considering the above, there are several important features that municipalities and industrial facilities should look for when implementing a protection relay. At Schneider Electric, the following is recommended:

• Easy-to-use: a protection relay should save time and money with simplified configuration and operating processes. Our Schneider Electric Easergy P1 protection relay can be configured with an HMI and mounted in a matter of seconds with spring clips. Easy operation with a built-in, dedicated circuit breaker control.

Versatile: it should be optimised for MV protection on over-current, voltage, and/or frequency and serve as the main protection on LV applications when ANSI functions are required. Support for serial communications ensure integration with control systems, providing operators with accurate information at critical times.

Flexible: it should be optimised for compact switch gears and offer graded functionality tailored to specific applications. In a nutshell, its design should allow for a variety of new and retrofit installations. The Easergy P1 can be used in a feeder, motor, or generator application.

Enhanced safety and reliability: an insulated casing and non-volatile memory for settings and records as well as clock retention (for three days) is provided, at minimal power consumption.

In the case of our P1 protection relay, it features a plastic casing which prevents corrosion due to humidity and chemicals. Furthermore, the P1’s small size of 106 x 106 mm translates into it taking up very little space whilst still playing a vital role in keeping facilitates safe.

Ultimately, protection relays are a non-negotiable part of any electrical system, providing operational stability and, more importantly, safety.


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