Residual Current Devices (RCDs) are a critical component of earth leakage protection systems. The technology dates back more than 60 years, but has evolved into 4 different types of RCD as industrial and commercial applications and energy needs have changed. Here’s a guide to these different types and their uses, from power quality audit specialists and suppliers of commercial earth leakage relays.
The Importance of RCDs
RCDs are safety switch devices usually found as components in earth leakage protection systems alongside earth leakage relays and other protective devices. They protect against faults and provide fire protection by preventing dangerous sparking on the electrical network.
#1 – Type AC Residual Current Devices
Selecting the right RCD is about matching the device to the load. As a result, type AC RCDs are used there the fault current is sinusoidal at the same frequency as the supply. They are usually part of the earth leakage protection system where the load is resistive or linear, and are the most common type of RCD.
#2 – Type F
Type F RCDs are utilised in earth leakage protection systems where composite residual currents are likely, such as on electrical networks with heat pumps or HVAV systems where single-phase motors are being controlled by a variable speed drive. These RCDs can also detect the same residual currents as Type A RCDs.
#3 – Type A
These are commonly used on circuits that have AC and DC power where a pulsating DC residual current is likely. It can also detect the same residual current issues as Type AC units.
#4 – Type B
Certain types of medical equipment, air conditioning systems, electric vehicle chargers and pumps utilise a 3-phase motor on a variable speed drive, which can cause residual currents at frequencies greater than 50Hz, non- sinusoidal elements, smooth DC waveform and other issues. For this, a Type B RCD is needed, which can detect all of the above as well as covering the same detection as Type F.
In addition, there is a fifth RCD type called Type SI, which is fairly new to the market. These are designed to offer the most advanced protection for earth leakage applications and offer the highest surge current capability as well as being able to operate in particularly demanding environments.
Advanced Earth Leakage Protection Systems and Earth Leakage Relays from Power Quality Audit Specialists
At Quality Energy, we work with commercial and industrial clients of all sizes to provide state-of-the-art earth leakage protection and monitoring systems that are scalable, customisable and reliable. Our power quality audit process will help you uncover problems within your electrical network to ensure a custom and cost-effective solution can be designed for your facility’s needs.
To find out more about our earth leakage protection systems and earth leakage relays, or to have our expert team perform a power quality audit of your facility, please contact us today.
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