Residual Current Monitoring in an Industrial Environment
We're wrapping up our series on Condition Monitoring, by discussing Residual Current Monitoring (RCM) as an essential system to implement in any industrial environment. By monitoring the state of the electrical system in a facility, RCM assists in detecting faults early – reducing downtime and saving money.
Catch up on previous articles in our Condition Monitoring series:
Part 1:The benefits of a condition monitoring system
Part 2: Vibration monitoring
Part 3: Vibration monitoring continued
Part 4: An overview of motor circuit analysis
In this fifth and final article in the series, we outline Residual Current Monitoring by discussing what it entails, and the advantages of implementing it in your facility.
What is residual current?
Residual current is an electric current that flows briefly in the circuit after the voltage has been reduced to zero. This is due to the momentum of charge carriers.
What is Residual Current Monitoring?
Residual Current Monitoring (RCM) is implemented in an earthed electrical systems to continuously monitor the fault of residual current levels. It monitors the network continuously for faults, and generates an alarm when these occur.
Examples of situations that may generate an alarm are:
- Insulation damage or degradation
- Wiring errors
- Neutral-to-ground faults
- Connection of defective devices
- Minute leakage currents that are unable to be picked up by fuses or circuit breakers
What are the advantages of Residual Current Monitoring?
- Ensures preventative maintenance can occur before an expensive breakdown happens.
- Provides protection for the whole electrical system as well as other electrical devices that are installed.
- Collection of valuable data from the electrical system.
- Preventative electrical safety for both man and machine.
- Reduces operating costs and cost risks.
What is the significance of RCM in industrial environments?
1. Optimised Maintenance:
- Information is obtained immediately by centralised or distributed alarm messages.
- Planning of time and personnel resources can be done efficiently and effectively through complete documentation and precise location of the fault.
- The use of remote diagnostics and administration will ensure preventative intervention over a LAN network.
2. Increase Fire Protection:
- Detection of potential fire hazards caused by high fault currents.
- Indicating a neutral conductor overload or interruption at an early stage, thus preventing material damage.
3. Higher Operational and System Safety:
- Provides preventative safety, for both man and machine, against the hazard of electrical current.
- Monitors insulation deterioration continuously.
- Detects potential faults when commissioning new electrical installations.
- Alarm messages are sent for signalling or switching off the system.
4. Improved Economic Efficiency:
- Reduction of maintenance and operating expenses.
- Unplanned system downtimes can be avoided through information obtained at early stages.
- Increase in productivity due to operational reliability.
- Detection of weak points in the electrical system will assist in investment decisions.
5. Comprehensive Information:
- Information is displayed clearly on Liquid Crystal Display (LCD).
- Easily integrated into a facility management system.
What is a Residual Current Monitoring device?
A Residual Current Monitor is used to measure residual current. If there is an increase in the residual current, it can be detected and reported at an early stage. As seen in the figure below, the residual current monitor cannot independently interrupt the supply line. A differential current is measured and is sent out by a suitable interface. These devices also have one or more relay outputs that can be used to control circuit breakers.
What components are used in a Residual Current Monitoring system?
A typical residual current monitoring system, as seen in the image below, consists of the current measuring device, relays, circuit breakers and a display.
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