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GENERAL GUIDELINE FOR ELECTRICAL TESTING ENGINEER

Testing Guidelines

• Protection scheme shall operate correctly at critical time of fault in system and also it shall avoid tripping of healthy system/elements. Testing of Protection scheme is carried out for verification of scheme for intended operation and as confirmation of healthiness of protection scheme.

• Protection engineers should have appropriate engineering skills with an emphasis on electrical power engineering with knowledge of communication and IT systems is also required. This provides the basic knowledge that is a prerequisite for understanding the principles and techniques of power system protection. However, recently recruited protection engineers will need further training and experience before they can be expected or allowed to work unsupervised in the field of protection.

• Enhanced functionality of numerical protection devices based on microprocessor technologies lead to an increased number of setting parameters and the use of flexible products based on a manufacturers own common hardware platform, with different software or firmware modules and algorithm of operation.

• Protection engineers shall study protection devices manual for better understanding of given protection relay function behavioral in particular power system event. This can enable him to do better parameterization and configuration of devices.

Commissioning Testing of Protection System

I. Protection and control scheme with all interlock conditions, covering all practical possibilities shall be verified to ensure correct operation.

II. All circuits given in approved drawing shall be checked thoroughly. A logic check list also can be prepared for differently feeder types. 

III. If any Issues/Rectification/Correction found in drawing scheme at time of testing; it shall be coordinated to corporate office (Testing Unit / Engg Cell)

IV. Parameter settings and configuration shall be verified first and it should according to GETCO protection philosophy and protection system requirements.

V. Protection function shall be verified by simulating all possible power system events related to that function.

VI. Protection trip shall be verified each of 6 trip coils operation in EHV bay along with TBC tripping logics incase of 3-bus sytem.

VII. Auxiliary circuits (i.e. auxiliary relay operation, inputs to other devices, LEDs/Indication/Ann. Circuits) triggered by function under test also, shall be varified.

VIII. If SCADA substation then alarm event generation in HMI along with Text and profile state shall be checked.

IX. DR shall be checked to further varify function operation as per parameterisation and visiblity of necessary digital channels related to that function.

Example : While checking auto recloser function operation following shall be varified in DR:

- Single pole trip command with pulse duration

- Opening of CB pole (Only single pole for which fault simulated)

- Dead Time duration in DR apparent as per setting

- A/R close command and it’s pulse duration

- Closing of CB

- Three pole trip (If AR blocked / lockout)

- Visbility of AR blocked channel

- Visibility of fualty phase trip command

- Visibility of Carrier Signals

- Visibility of fault in Zone etc.

X. At time of BB/LBB protection testing, presence of at least two protection engineers is highly recommanded. Before starting testing it shall be ensured that any undesired tripping does not occure. Protection engineers shall ensure isolation of necessary links/fuses and varify CT Selections physically (i.e. visually or electrically) and in device input native nodes.

XI. After completion of testing protection engineers must ensure to undo all the temporary changes made i.e. in settings/configuration/control circuits/extending temporary loops etc.

XII. Finally verify that physical status of switch yard elements, CT/PT selection, switches position/selection (AR/Carrier/NIT) and isolation links/fuses (CT-PT and other circuits) are in state/position as per service requirement.

XIII. Final configuration settings in relays shall be extracted and verified that they are as per philosophy and system requirements before putting element in service.

Routine Testing of Protection System

I. Ensure outage procedure is completed, until than any work shall not be initiated.

II. Verify status of all bay equipment and it’s auxiliaries along with CT/PT selections. Also, before testing, online monitoring can be utilized for verification of protection system inputs.

III. Check if any network configuration related to setting requirement changed to updates settings as mentioned. Testing shall be done to validate relay configurational changes made.

IV. After writing relay parameter/configuration, reading of parameter/configuration shall be performed to verify changes made are successfully written.

V. Before starting testing all precautionary measures shall be ensured

i. Check if isolation is required to be made conidering - SPS, CT Series to other devices, possibility of LBB protection operation etc.

ii. Kit supply and safety, Kit Connection to CT/PT circuits, sensing/feedback inputs etc.

VI. Measurment test can be performed for verification of kit connection with lower current and voltage values.

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