DL/T 487-2024 in English

VALID

Guidelines for measuring distributed voltage of insulator strings on 330 kV and above AC overhead transmission lines

Issued on:2024-12-25
Implemented on:2025-06-25
File Format:PDF
Delivery:RFQ

Price(USD)： RFQ

Standard No:	DL/T 487-2024
Document status:	VALID
Title in English:	Guidelines for measuring distributed voltage of insulator strings on 330 kV and above AC overhead transmission lines
Title in Chinese:	330kV及以上交流架空输电线路绝缘子串分布电压测量导则
Language:	English
File Format:	Electronic (PDF)
Delivery:	RFQ
Issued on:	2024-12-25
Implemented on:	2025-06-25
ICS Classification:	29.080.10-Insulators
Chinese Classification:	K48-Insulator
Professional Classification:	DL-Electricity
Related Keywords:	distributed voltage distributed voltage curve case digital distributed voltage meter total voltage different voltage levels

Introduction

Analysis of Standard Technology Evolution

DL/T 487-2024 is mainly upgraded compared with the 2000 version: new technical requirements for distributed voltage measuring instruments (4.2 items), introduction of the concept of phase difference coefficient (3.2 items), expansion of 750kV data (Appendix B), and deletion of theoretical voltage conversion coefficient calculation. It reflects the new requirements for insulation detection accuracy in the development of UHV power grid.

Core Measurement Technical Specifications

Key Parameters	Field Measurement	Laboratory Measurement
Probe Capacitance	<10pF	<4pF
Input Resistance	>5000MΩ	>10000MΩ
Environmental Humidity	<80%	10-40℃
Repeat measurement	Average of bidirectional measurement	U₀=100kV benchmark

Criteria system for degraded insulators

Degradation is determined when the following situations occur:
1) Measured value < 50% of typical data (e.g. 330kV first piece < 9.5kV)
2) A "V"-shaped mutation occurs in the distributed voltage curve
Case: On a 500kV line, the voltage of the 7th piece detected changed from 12.5kV to 5.8kV, and the adjacent 6th/8th pieces maintained at 13.5/12.0kV

Typical data application guide

Appendix B provides data rules for different voltage levels:
330kV The first three pieces on the conductor side bear about 28% of the total voltage
750kV The voltage of the first piece reaches 25.5kV (37 pieces in a string)
The middle phase insulator needs to be multiplied by the phase difference coefficient of 1.10

Implementation suggestions

It is preferred to use a digital distributed voltage meter with an input capacitance of <5pF
Robot measurement is recommended for lines above 750kV (Article 5.2.2)
Establish a historical data comparison library and pay attention to the characteristics of the V-shaped curve
In high-altitude areas, adjust the length of insulating tools according to DL/T1634

More samples: YD/T 3934-2021 DL/T 5154-2012 JC/T 2453-2018

Sample only — not a preview of DL/T 487-2024