Protective Relay Calibration & Programming
Various classes of tests can be made each with varying degrees of complexity. It is most important that all tests be geared to the objectives which they are intended to meet and that they be streamlined within these objectives. Well defined testing for maximum performance is our recommendation.
The objective of protective relay testing indicates four classes of tests. These are:1.) Acceptance Tests
a. New Programmable Relay First Time Applied
b. Test on each Product Received
2.) Installation Tests
3.) Maintenance Tests
4.) Repair Tests
Acceptance tests are done once and generally on the bench in the shop or at the customer’s location. These separate into the two types shown. On (A) new products which have not been previously used, extensive testing on a programmable type relay may be desired to prove it, gain experience and knowledge, and/or additional technical application information. The second type (B) test on each protective relay received from the manufacturer should be streamlined to include only important practical check points to assume that the product is working correctly and up to the manufacturer’s standards.
Installation tests are field tests to determine that the installation will perform correctly in actual service. These are not repeated on any given installation unless incorrect operations have occurred. Most frequently they are performed by simulated tests with the secondary circuits energized from a portable test source. Other methods include (1) simulated tests using primary load current, (2) operating tests with the primary energized at reduced voltage, and (3) staged secondary fault tests. Staged fault tests actually apply secondary faults to the power system for checking the relay operation. Usually several faults, both internal and external, are applied. Therefore, staged fault tests are limited to very complex utility installations.
One of the most important tools in installation or troubleshooting is the automatic event recorders and/or data storage devices. Several of these judiciously placed around the system are invaluable in times of trouble and may save many man-hours of conjecture. The desire is to obtain a record of conditions which will indicate the source of trouble, but they can be equally valuable in indicating what the problem was not.
Maintenance testing generally is done in the field at regular intervals. A recent IEEE survey indicates that a large majority of customers do maintenance testing once a year. According to the IEEE Survey, relay maintenance generally consists of:
1.) Inspection and burnishing of contacts (old electromechanical style of relays).
2.) Automatic self test of relay.
3.) Adjustments checked.
4.) Breakers tripped by manual contact closing.
5.) Screws checked for tightness.
6.) Covers cleaned.
7.) As Found and As Left tests made
Repair testing as the name implies involves recalibration after major repairs have been made. Thus, these tests are usually made in the repair shop. Many minor repairs frequently are done in the field during maintenance and need not involve complete recalibration. You can find more informatio on relays on www.RelayTech.co
