The LRM 200 is a microprocessor-based, true DC micro-ohmmeter designed to test the contact resistance of circuit breaker contacts, switchgear, and bus bar joints. It is the instrument every test technician needs to have to maintain circuit breakers, switch gear and busbars. The LRM 200 is designed to meet the IEEE C57.09-1999 standard’s requirements for testing circuit breaker contact resistance.
The LRM 200 also meets the requirements of IEC 6227-100 (For GIS), IEC6227-200 (For HV switch yard). The LRM 200’s wide measuring range is 1 micro Ohm to 5 Ohms with 0.1 micro-ohm resolution with a current range of 10 A to 200 A. The LRM 200 injects a true DC current through the contacts under test and measures the contact resistance.
During the test, only one end of the Circuit breaker is grounded for accurate measurement. The LRM 200 can perform CB testing in Dual Ground mode. In Dual Ground mode, both sides of the CB are grounded. Some current is diverted to the ground via a ground cable. An external current sensor connected to the ground cable provides input to the LRM 200 which eliminates the effect of the diverted current and produces accurate readings.
As the rise and fall time is configurable for each test, no transients are induced in the associated apparatus such as current transformers. This avoids maloperation of the connected relays to the current transformers. LRM 200 provides audible signal when test is in progress. LRM 200 provides continuous dc output without overheating. Built in thermal sensor protects LRM 200 overheating if the temperature excess 850 C.
The unit’s back-lit color LCD touchscreen (800 x 480 pixels) is viewable in bright sunlight and low-light and provides an intuitive menu structure where running a test is just few taps away. The full-sized industrial keyboard makes data entry quite easy for information such as nameplate and setting information.
