Micro Ohmmeter

By Author: millin lange
Total Articles: 10
Comment this article

It is designed for testing EHV circuit breaker contact resistances, bushing contact joints, welding joints, or for any low resistance measuring application. This high current and very lightweight (16.8 lbs/ 7.6 Kg) micro ohmmeter is designed to meet the IEEE C57.091999 (5.15) requirement for testing circuit breaker contact resistance. The tester can accurately measure resistance values from 1 micro‐ohm to 5 ohms. A 0.1 micro‐ohm resolution is possible with current greater than 5A. This device applies a selectable true DC test current from 1A to 200A to the resistance load to be tested. It controls the test current’s rise and fall rates.

The test current rise and fall rate can be selected from 5 seconds to 10 seconds. An “Auto Test” mode is also available and can be initiated simply by applying the sense cables’ leads across the two points of interest in the current path. This feature is very convenient when measuring a sequence of several resistance values in a circuit breaker contact. It can also compare test results against preset limits and determine if a test passed or failed, and a “Pass” ...
... or “Fail” flag is displayed accordingly.

Since a true DC current (with controlled rise/fall time) is passed through the circuit breaker contact, no magnetic transient is induced into the breaker’s current transformers. This feature greatly reduces the risk of inductively trip‐ping a breaker control (bus differential relay). With the Dual Ground option can also measure the circuit breaker contact resistance with both sides of the breaker bushing being grounded. When a test current is applied to a circuit breaker with both sides grounded, some of the test current flows through the safety ground cables. Using an external current sensor, the tester measures and eliminates this current from the total test current, then calculates the actual resistance value of the circuit breaker.

The device features a back‐lit 128 x 64 pixel LCD screen that is viewable in both direct sunlight and low‐light levels. The resistance readings are displayed on the LCD screen in micro‐ohms or milliohms. The unit is operated via a convenient 44‐key “QWERTY” keypad on the front panel. It can store 128 records of 64 readings internally, and up to 999 test records on an external USB Flash drive. Test header information (Company, Substation, circuit breaker ID’s) can also be entered using the 44‐key keypad and is stored with each test record.

Analysis software is provided with each unit and can be used to remotely control the tester via the RS‐232C port. Using this software, the user can retrieve test records (from the unit’s memory or a USB Flash drive), analyze test results, and print test results on a desktop printer. Test records can also be exported to PDF, Excel, and XML formats.

This content has been taken from http://www.ideamarketers.com/?articleid=3291235&CFID=185812220&CFTOKEN=42417219

The company which manufactures electrical equipment for measurement and maintenance of electrical substations offers customers reliable equipment. We have a wide range of products like micro ohm meter, power analyzers, ultrasonic leak detector, transformer test equipment or test equipment for relays. For further information about circuit breaker tester, please visit us online at http://www.amperis.com/en/products/microhmmeters/.