What Are The Main Types Of Rcd? Overview Of Working Of Rcd With Detail

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A mechanical switch having the residual current tripping feature is called an RCD (Residual Current Device). The circuit is only broken when a leakage current flows to the earth. The timing of the voyage is intended to reduce the dangers to human life. The original RCD was invented at an unknown time and by an unknown person, but it unquestionably hit the market in the 1950s.

RCDs are currently widely utilized throughout much of the world; in some situations, their usage is required, while in others, it is not. The devices listed below are RCDs with extra features and functionalities that provide practical solutions for various applications.

Different Types of RCD

A device that incorporates residual current protection following one of the following standards is referred to as a residual current device.

A type

A-type RCDs are not sensitive to impulsive currents up to 250 A peak current (8/20 waveform). It is beneficial for safeguarding systems with electronic components for current or phase adjustments of physical quantities (speed, temperature, light intensity, etc. ) supplied directly from the mains and insulated class I.

Type F

A new RCD type, Type F RCDs, was added to IEC 62423 and IEC 60755. Type F RCDs have the same detecting abilities as type A RCDs and are specifically made to safeguard circuits when single-phase variable-speed motors are in operation. These circuits’ residual current waveforms might combine many frequencies, such as line frequency, converter switching frequency, and motor frequency.

Frequency converters are increasingly used in some loads (washing machines, air conditioners, etc.) for energy efficiency, and type F RCD will cover those new applications. Additionally, Type F has improved disturbance tolerance qualities. They can trip even when a sinusoidal or pulsed D.C. differential current is overlaid with a pure direct current of 10 mA.

Type AC

RCDs of type A.C. look for lingering sinusoidal alternating currents. Most applications in practice are covered by type AC RCDs, which are acceptable for general usage.

Type B 

RCDs of type B can detect smooth D.C. residual currents, sinusoidal A.C., and pulsating D.C. in addition to composites of multiple frequencies. Additionally, several frequencies between 50Hz and 1kHz are used to determine tripping situations. An A.C. distribution network and a three-phase rectifying circuit can use single-phase rectifiers to produce pure D.C. residual current. Loads using three-phase rectifiers, such as variable-speed motors, P.V. systems, E.V. charging stations, and medical equipment, are intended for Type B RCDs.

B+ type

As with type B residual current protection devices, type B+ residual current protection devices are primarily designed for systems running on alternating currents. If they are below a tripping threshold of 420 mA, residual current protection devices of type B+ can be set to trigger for frequency ranges up to 20 kHz. Type B+ is now only mentioned in a German specification called DIN VDE 0664-100. Since the Association advises them of German Insurance Companies, Type B+ is typically employed to prevent fire protection risk.

Read More: Digital Power Meter: Advantages And Disadvantages of Digital Power Meter

Type with independent of voltage

Voltage-independent RCDs work by tripping the mechanism directly when the earth fault current passes through them. This RCD works independently of the mains voltage thanks to the output from the sensor coil, which activates a specifically designed magnetic relay and releases the RCD mechanism.

Normally, polarised (field weakening) relay construction is used in voltage-independent RCDs. This works by canceling the permanent magnetic flux by the excitation flux, which keeps the relay ON (produced by the fault current). Due to the magnetic flux being strengthened during the other half cycle can only happen during a one-half process of the a.c. Supply. Operating periods at the rated tripping current can range from 20 to 120 ms.

How do RCDs work?

An RCD will activate and cut off the power to the circuit if an earth leakage current of a specific nominal value results in an imbalanced current flow in the live conductors of the course. RCDs can trip below their designated little tripping wind (In), but they can also do so. For example, a 30 mA RCD must trip at a current between 18 and 28 mA.

It’s crucial to realize that RCDs cannot regulate voltage or current; instead, they offer safety by controlling the amount of time a particular maximum current may flow to the earth. The vector sum of the currents flowing in all active conductors through a working circuit should be nominally zero. A device trips when a circuit defect results in electricity flowing to the ground, which generates an imbalance.

How to use guides for various RCD kinds?

The most widely used RCDs in Australia are Type A.C. Residual Current Devices (RCDs). Type AC RCDs can trip the remaining sinusoidal alternating currents. However, there are now more D.C. Waveforms on the A.C. Supply because of the rising adoption of electronics, renewable energy, and other developing technologies. According to the updated clause 2.6.2.2.2 of AS/NZS 3000:2018, Type AC RCD installations won’t be authorized in Australia after 2 April 2023. This provision also mandates that all live (active and neutral) conductors be interrupted by RCDs placed next to or into socket outlets.

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