Siemens 7sg15 microtapp Operation Manual page 103

7SG15 MicroTAPP Maintenance
1 Introduction
Voltage control systems are continually operative when in service. Any deviations in accuracy and control will
directly affect the customers connected to the controlled power system. The MicroTAPP relay is a maintenance
free relay, with no user serviceable parts.
Minimal checks by skilled personnel trained in relay operation and capable of observing all the necessary safety
precautions and regulations appropriate to this equipment can be carried out on the relay during normal
operation. Ensure that all test equipment and leads have been correctly maintained and are in good condition.
No specialist test equipment is required.
2 Tests
As the tests can be best carried out with the transformers on load, care should be taken to ensure that no
operation of the tap changers can take place when settings are changed. As settings will be changed for testing
purposes, the operational levels should be noted prior to testing.
3 Basic Level Set-Point
Use a good quality RMS measuring voltmeter to measure the incoming voltage transformer level. Reduce the
bandwidth control to ±1% and operate the BASIC control to confirm the upper and lower limits are correct.
4 Load Drop Compensation (LDC) Set-Point
Determine the site load, the LDC is calibrated for the full site loading (firm capacity), i.e. if a site is half loaded the
LDC effect will be halved. Reduce the bandwidth control to ±1%, turn the LDC control to zero and adjust the basic
setting until the relay UPPER deadband limit is reached. Increase the LDC control until the LOWER deadband
limit is reached. The effective LDC at this point is 2% and can be related to the dial setting to confirm the correct
effect.
5 Alarms
With the tap changer disabled alter the basic setting to allow the relay to read low. Check operation of alarm
contacts.
6 Completion
On completion of tests all settings can be returned to normal.
©2013 Siemens Protection Devices Limited Chapter 8 Page 3 of 3