Hello friends, welcome in informationmania today here we are going to discuss about Types of Insulation Resistance Test and also learn how it’s works in details.
The Insulation Resistance Test is the second test required by the electrical safety testing standards.
The Insulation Resistance Test consists in measuring the Insulation resistance of a tool under test, while phase and neutral are short-circuited together. The measured resistance has got to be above the indicated limit from the international standards.
To measure a high-value resistance, techniques for measuring a coffee value current are used. a continuing voltage source is applied to the resistance to be measured and therefore the resulting current is read on a sensitive ammeter circuit which will display the resistance value.
Two sorts of ammeter circuits are used on our range of insulation resistance tester, each circuit being chosen to count on the resistance values to be measured.
Its objective is to live the ohmic value of the insulation under an immediate voltage of great stability, generally 50, 100, 250, 500, or 1000 VDC.
To evolve to specific standards, the insulation resistance test is often performed under voltages up to 1500VDC. thanks to the steadiness of the voltage source, it’s possible to regulate the test voltage by steps of 1 volt.
The stability of the voltage is critical; a non-regulated voltage will drop sharply in presence of nasty insulation which can cause an erroneous measurement.
Also, learn –
SHUNT AMMETER CIRCUIT
This circuit is employed for the current measurement of high values which correspond to resistance measurement of low values (l x l04 Ω to 2.106 Ω).
FEEDBACK AMMETER CIRCUIT
This circuit is that the one mostly used on our instruments. It covers the resistance measurement of high values above 2.106 Ω.
The input current flows through the feedback.
HIGH-VALUE RESISTANCE MEASUREMENT
Using a constant voltage source offers the advantage of defining with accuracy the worth of voltage used for the measurement. the selection of this voltage is a crucial parameter.
Indeed the worth of a high resistance depends on the voltage applied thereto. Other factors intervene within the high-value resistance measurement.
Temperature and ratio are two important parameters that influence the resistance value of an insulator. we provide on the newest Sefelec model the measurement of those two physical parameters (M1501P). 0n the subsequent table one can find the approximative resistance value of insulating materials.
In order to attenuate leakage currents, we provide a guard connection. The guard circuit allows us to scale back interferences on the test sample.
A terminal accessible on the front panel of our instruments allows the measurement of 1 of the resistance of a Delta configuration (i.e. a cable with two conductors and its external shielding), in order that the result’s not suffering from the presence of the opposite two shunt resistances.
Why Insulation Resistance Test is Done?
• Electrical stresses: Mainly linked to overvoltage and under-voltage.
• Mechanical stresses: Frequent start-up and shutdown sequences.
• Balancing problems on rotating machinery and any direct stress to the cables and therefore the installations generally.
• Chemical stresses: The proximity of chemicals, oils, corrosive vapors, and mud, generally, affects the insulation performance of the materials.
• Environmental contamination causes an aging acceleration of insulation.