Continued from first part: Measurement of insulation resistance (IR) – Part 1 1. IR Values For Electrical Apparatus & Systems (PEARL Standard / NETA MTS-1997 Table 10.1) Max.Voltage Rating Of Equipment Megger Size Min.IR Value 250 Volts 500 Volts 25 MΩ 600 Volts 1,000 Volts 100 MΩ 5 KV 2,500 Volts 1,000 MΩ 8 KV 2,500 …
Measurement of insulation resistance (IR) – Part 1
Introduction The measurement of insulation resistance is a common routine test performed on all types of electrical wires and cables. As a production test, this test is often used as a customer acceptance test, with minimum insulation resistance per unit length often specified by the customer. The results obtained from IR Test are not intended …
Direct On Line (DOL) Motor Starter
Different starting methods are employed for starting induction motors because Induction Motor draws more starting current during starting. To prevent damage to the windings due to the high starting current flow, we employ different types of starters. The simplest form of motor starter for the induction motor is the Direct On Line starter. The Direct …
Erection Procedures For Medium Voltage Switchgear
Before commencing erection of medium voltage (MV) switchgear check that all connections are tight on busbars and on main and auxiliary circuits. Examine the insulation carefully, because there have been cases of burned out connections due to failure to observe this precaution. Obvious faults such as distorted panel work, broken meter glass and damaged packing …
Inspection of electrical installations in home (part 2)
Continued from part I – Inspection of electrical installations in home (part 1) Is a Periodic Inspection Needed? Every installation deteriorates with use and age. Therefore, one must ensure that the safety of users is not put at risk and that the installation remains in a safe and serviceable condition. Let’s have a closer look …
Inspection of electrical installations in home (part 1)
Europe has an ageing housing stock. There are many homes with outdated wiring. This wiring is deteriorating, has been inappropriately amended, or is insufficient for the electrical loads of today’s typical household. Many of the homes have not undergone any renovation of the electrical installation even though the use of electricity in these homes has …
Sudden pressure relay in oil-filled power transformer
Internal arcing in an oil-filled power transformer can instantly vaporize surrounding oil, generating gas pressures that can cause catastrophic failure, rupture the tank, and spread flaming oil over a large area. This can damage or destroy other equipment in addition to the transformer and presents extreme hazards to workers. Modern sudden pressure relays consist of …
220V DC System at Thermal Power Station
The 220V DC system supplies direct current as source of operating power for control, signaling, relays, tripping and closing of switchgears, emergency motors of most important auxiliary systems. Under normal conditions of station generation, the storage battery units are kept floating in DC bus bars by means of the trickle chargers (also known as float …
Purpose and maintenance of transformer bushings
The two most common types of bushings used on transformers as main lead entrances are solid porcelain bushings on smaller transformers and oil-filled condenser bushings on larger transformers. Solid porcelain bushings consist of high-grade porcelain cylinders that conductors pass through. Outside surfaces have a series of skirts to increase the leakage path distance to the …
Retro perspective 30 years ago: Metal-Clad or Metal-Enclosed MV Switchgear? What to choose?
There are two types of switchgear commonly applied today for switching and protection of in-plant medium voltage (4.16 kV through 34.5 kV) power distribution systems. One is metal-clad switchgear using draw-out air-magnetic or vacuum circuit breakers and relays for both load switching and fault protection: the other is metal-enclosed switchgear using interrupter switches for load switching …
