NB/T 11307.2-2024 in English

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Standard No:	NB/T 11307.2-2024
Document status:	VALID
Title in English:	Guidelines for fire hazard assessment of power equipment and materials Part 2: Oil-immersed transformers
Title in Chinese:	电力设备与材料着火危险评定导则第2部分：油浸式变压器
Language:	English
File Format:	Electronic (PDF)
Delivery:	Via email within 2~4 business days
Issued on:	2024-09-24
Implemented on:	2025-03-24
ICS Classification:	29.035.99-Other insulating materials
Chinese Classification:	K15-Electrical insulating material and its products
Professional Classification:	NB-Energy
Related Keywords:	fire hazard assessment five-level fire hazard assessment system key tolerance band unspecified fire hazard level class material fire protection classification system take silicone rubber 11307.2-2024 international standard arc energy classification class

Introduction

Analysis of the technical framework of the standard

Core chapters	Key technical points	Innovation requirements
Chapter 4 Solid Insulating Material Tests	Horizontal/vertical burning test methods, sample preparation specifications	Thickness tolerance classification control is clarified for the first time (0.02-0.5mm)
Chapter 5 Flash Point Determination	Pensky-Martin closed cup method, atmospheric pressure correction formula	Flash point ≥135℃ (10℃ higher than the international standard)
Chapter 6 Arc Test	Energy classification (2-27MJ), electrode structure design	Introduction of a five-level fire hazard assessment system

The standard innovatively proposes a three-dimensional evaluation system for arc tests on oil-immersed transformers:

Energy control: 6 energy thresholds are divided according to voltage levels (66kV/2000kJ to 750kV/27000kJ)
Safety protection: Containment area diameter ≥ 5 times equipment size + 5 times height
Monitoring requirements: 50kHz sampling rate pressure sensor + 2000fps high-speed camera

Take silicone rubber as an example of dual evaluation requirements:

Test type	Qualified index	Actual application case
Horizontal combustion	HB grade (burning rate ≤75mm/min)	Bushing seals meet the standard by adding aluminum hydroxide flame retardant
Vertical combustion	V-0 grade (single afterflame ≤10s)	Ceramic silicone rubber technology is used for the insulation cylinder of the tap changer

The arc test area should be equipped with an oil drain pool (volume ≥5m³) and an explosion-proof monitoring system
The combustion test chamber needs to maintain a constant temperature and humidity (23±2℃, 50±10%RH)
Equipped with 0.1-level current transformer and 0.2-level voltage transformer

Use natural ester insulating oil (flash point ≥300℃) to replace mineral oil
Add a directional flow guide structure to the pressure release device (reduce V-level risk)
Add nano-grade flame retardant filler to epoxy resin parts

Compared with IEEE C57.156-2016, this standard mainly improves:

Comparison Dimensions	NB/T 11307.2-2024	International Standard
Arc Energy Classification	Class 6 (including 750kV equipment)	Class 4 (up to 500kV)
Specimen Thickness Control	Class 13 Tolerance Band	Unspecified
Fire Hazard Level	Class 5 Evaluation System	Class 3 Classification

More samples: GB 50021-2001(2009) NB/T 47013.2-2015 GB 18306-2015

Sample only — not a preview of NB/T 11307.2-2024

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