Handheld loop resistance testers must be tested on-site in strict accordance with current industry standards and safety regulations to ensure safe testing, accurate data, and compliant results. The testing procedures mainly cover four aspects: instrument standards, equipment testing standards, on-site operating procedures, and pass/fail criteria. The core basis is current standards such as DL/T 596-2021 and DL/T 845.4-2022.
I. Core Testing Standards
(I) Instrument Standards
DL/T 845.4-2022 specifies the technical requirements, test methods, and inspection rules for loop resistance testers, clarifying core indicators such as test current, accuracy, and electromagnetic compatibility; JJG 1052-2025 applies to digital loop resistance testers with a rated operating current of not less than 100A, specifying the items and error limits for initial verification, subsequent verification, and in-use inspection, and clarifying the verification cycle as once a year; DL/T 967-2005, as a supplementary standard for the power industry, further standardizes the instrument verification process and technical requirements.
(II) Equipment Testing Standards
DL/T 596-2021 clarifies the test cycle, test methods, and acceptance criteria for the circuit resistance of various types of power equipment, stipulating that the test cycle for equipment of 330kV and above shall not exceed 3 years, and for equipment of 220kV and below, it shall not exceed 6 years, and testing is required after Class A maintenance; GB/T 11022-2020 defines the limits and test methods for the circuit resistance of high-voltage switchgear; DL/T 618-2019 clarifies the specific details of circuit resistance testing for on-site handover testing of GIS equipment, ensuring the compliance of GIS equipment testing.
II. On-site Test Operation Specifications On-site tests must strictly adhere to the principles of “safety, standardized operation, and accurate measurement.” The specific procedures and requirements are as follows:
(I) Pre-test Preparation First, execute the power outage, voltage testing, discharge, and grounding procedures. Install grounding wires with a cross-sectional area of not less than 25mm² on both sides of the equipment under test to ensure the equipment is in a de-energized state. Check the test environment: temperature should be controlled between -10℃ and +40℃, relative humidity should not exceed 80% and there should be no condensation. Avoid areas with strong electromagnetic fields to prevent interference with measurement data. Check the instrument status, confirming that the battery is fully charged, the test leads are intact, and the instrument has been calibrated and is within its validity period. If the switch under test is electrically operated, measurement must be performed after electric closing. For manually operated switches, confirm that manual operation is permitted. Before measurement, the switch can be switched on and off several times to break the oxide film on the contacts, ensuring good contact and reflecting the actual operating conditions. (II) Wiring Operation A four-wire wiring method is used. The red and black current wires are clamped at both ends of the device under test, and the yellow and green voltage wires are clamped inside the contacts, avoiding the current path. Ensure the voltage wires are in close contact with the contacts under test to eliminate the influence of test lead resistance and contact resistance. When wiring, ensure the wires are short and thick, with good contact, to avoid data distortion due to improper wiring. If the switch has main and auxiliary contacts or parallel branches, each pair of contacts must be measured separately. Thin insulating material should be placed between non-tested contacts to prevent mutual interference. Simultaneously, the switch tripping mechanism should be locked to prevent sudden tripping during testing and damage to the instrument.
(III) Parameter Setting and Testing
After powering on, select the appropriate current range (standard 100A) and test time (standard recommendation 10-60s) according to the type of equipment under test and standard requirements to ensure stable test current output. Start the test with one button. Record the data after the reading stabilizes. Closely observe the instrument status during the test. If overheating or overcurrent alarms occur, stop the test immediately, troubleshoot the fault, and then restart the test. After each test, wait for the instrument to discharge completely before disconnecting the wiring to avoid the risk of electric shock.
(IV) Post-Test Cleanup
After the test, disconnect the test leads, restore the original wiring of the equipment under test, disconnect the grounding wire, and confirm that the equipment is in normal condition before ending the test. Export and store the test data promptly, labeling the test date, equipment name, test environment, etc., to establish a complete test file for subsequent traceability and comparative analysis. Clean and inspect the instrument, and store it properly to avoid damage. III. Test Pass/Fail Criteria The circuit resistance test results must be judged comprehensively based on the equipment manufacturer’s specifications and industry standards. The core criteria are as follows:
1. The circuit resistance value of the tested equipment must not exceed the manufacturer’s specified value. For circuit breakers, this is generally not more than 50μΩ～200μΩ; for disconnectors, it is generally not more than 100μΩ～300μΩ; and for GIS equipment, it is generally not more than 50μΩ. It must also comply with DL/T 596-2021, not exceeding 110% of the factory test value, with no significant difference between phases.
2. Compared with previous test values for the same equipment, there should be no significant increase (the increase should not exceed 20%). If a significant increase occurs, issues such as contact oxidation or loosening should be investigated and addressed promptly to avoid equipment failure.
3. Test data must be accurate, complete, and meet instrument calibration requirements. There should be no significant abnormal fluctuations, ensuring data traceability and verifiability.
Post time: Apr-27-2026