Services

Servicing and Support of MV Switchgear

Servicing and Support of MV Switchgear

Malaysian Switchgear (Pty) Ltd offers servicing and maintenance on all Tamco as well as other brands of switchgear.

Once all the essential testing has been completed, the switchgear is cleaned, removing all dust from the chambers and all necessary parts are lubricated. The voltage transformer secondary voltage is recorded to ensure the voltages are within specification.

It is important to note that some insurance companies require annual switchgear maintenance be carried out to ensure compliance with the parameters of your insurance schedule.

Calibration:

All of our testing equipment, which is valued at over R2 million, is calibrated on an annual basis by a registered independent calibration specialist to ensure accuracy.

Our services include:

    • Open gap vacuum testing on breakers (VI)
    • Speed Trace testing to check the open and closing time on the breaker (VI)
    • Secondary injection testing
    • Contact resistance testing on breakers (VI)
    • Function testing
    • Cleaning of circuit breakers (VI) and panels by using a compressor with a cleaning solvent
    • Greasing and oiling all parts that require lubrication
    • Optional extras – partial discharge testing

Vacuum Switchgear Servicing

Switchgear, unlike other mechanical and electrical equipment, remains inactive for long periods of time and may only be called upon to operate during fault conditions a few times in its lifespan. The critical issue is that prior to this fault condition there is no guarantee that the apparatus will function within its design specifications to clear a fault condition safely and effectively without conducting a maintenance programme. Any failure that may occur on the medium volt system that feeds a critical load such as data centres, banks, airports, container depots and hospitals, among others, have drastic consequences. A dangerous situation such as these can be averted with a scheduled maintenance programme.

It is possible to monitor some aspects of the equipment via building monitoring systems (BMS) or SCADA facilities such as battery tripping units, protection relay health status, tripping circuit integrity but there is no method available as yet that can ensure the apparatus will function correctly from initiation of a fault condition to the safe and effective clearance of the fault condition.

Most mechanical devices have various built-in methods to monitor their effective operation and processes and will – in most cases – emit some form of pre-failure warning sign such as excessive noise, smell, vibration. With switchgear the only way to detect a potential failure is to conduct tests to prove reliability and readiness for the day that a fault condition occurs.

The following tests and maintenance procedures are advisable for all MV switchgear:

  • Visual inspection
    • This is to determine that there are no visible signs that may lead to malfunction such as distortion of the panels, heat related discolouration, misalignment of circuit breakers, and ensuring that primary contacts are not distorted or discoloured
  • Operation or functionality checks
    • Opening and closing of the circuit breaker (mechanically and electrically)
    • The circuit breaker racking mechanism is smooth and direct
    • The earth switch is operating correctly
    • The status indication is correct (mechanical and electrical)
    • The spring charge sequence is correct and within the specified time frame
    • The mechanism latches as required
    • All three vacuum interrupters and actuators are functioning
    • The trip counter is functional

In addition to the above testing, power frequency is also assessed to ensure the integrity of the vacuum (open gap test) in the vacuum interrupter and the insulation resistance of the primary circuit insulation. Power frequency testing is done using a high AC voltage of 17-28kV respectively. To test and verify this, is a specialised equipment called a contact resistance tester is used.

Speed Tracing on Circuit Breakers

Speed tracing will determine the opening time of all three poles of the circuit breaker as well as the energising of the trip coil of the circuit breaker. Speed Tracing is conducted using specialised equipment called a Speed Tracer.

Secondary Injection Testing

Secondary Injection Testing (SIT) is one of the most important tests and is used to verify the accuracy and functionality of both the protection relay, the overall tripping time of the circuit breaker as well as the tripping circuit integrity.

SIT testing simulates the fault condition from the pickup of the relay to the clearing of the fault and logs the time of the complete operation. The accuracy of the protection relay (set tripping time) is compared to the standard tripping curve as supplied by the manufacturer and the result determines if the relay is still within the manufacturer’s specifications. SIT testing is also used to verify the accuracy of the ammeters and voltmeters.

Contact resistance

The resistance of the vacuum interrupter contacts as well as resistance of all joints in the primary circuit are tested to ensure good surface contact. Contract resistance is assessed using specialised equipment called a doctor tester.

Partial discharge

Partial discharge testing is otherwise known as conditional monitoring and will ascertain whether there is a partial discharge emitting from the primary insulation (bushings) or the cable terminations. Any discharge recorded above a specific level will indicate a possible flash over condition and can be rectified before this occurs.

Using our state-of-the-art equipment, we are able to check the partial discharge on switchgear, which is done live as the tester is then able to pick up discharge through the switchgear panel housing. PD testing is done every 6 to 12 months on clients request. We offer PD testing on circuit, cable housings and busbars chambers. If a client requests full service on switchgear PD testing is included.

NOTE: Partial Discharge testing does not form part of the standard maintenance routine but is normally offered as an addition to the routine maintenance procedure.