Definition and Important Test of Class 1E Industrial UPS in Nuclear Power Plant

Abstract: In nuclear power plant, there is only one nuclear safety level for electrical equipment, which is called 1E level. Other equipment is "out of class equipment". Class 1E equipment includes the equipment necessary to complete the following functions: 1. Automatic shutdown; 2. Containment isolation; 3. Emergency cooling of the core; 4. Heat export in the reactor and in the reactor building; 5. Prevention and limitation of radioactive release under accident conditions. The class 1E industrial ups of nuclear power plant belongs to this kind of electrical equipment. Because of the importance of its safe operation is self-evident, so it is all about reliability.


Key words: definition of class 1E industrial UPS in nuclear power plant, several important tests under extreme service conditions, 1. Electromagnetic compatibility test; 2. Test on the influence of temperature change on performance; 3. Test against mechanical vibration; 4. Test against earthquake. Introduction of class 1E industrial ups of AVIC-Tech nuclear power plant.


1. Definition of class 1E electrical equipment of nuclear power plant


The safety level of nuclear power plant equipment is divided into two categories.

1) The safety level of mechanical equipment is divided into four levels. Safety level 1 is the most important for safety, and the importance of level 2, 3 and 4 is decreasing in turn.

2) For electrical and instrument equipment, safety level, also known as 1E level, is no longer classified in safety level. For all kinds of safety level equipment, there are specific requirements in the aspects of design, manufacturing, test and inspection. It is also required to specify the corresponding design and manufacturing specification level, quality assurance level, exhibition resistance classification and environmental appraisal level to determine the safety level of the equipment and the safety and economy of the nuclear power plant There is an important impact, reducing the level will affect the safety of nuclear power plants, and improper upgrading will increase the cost of nuclear power plants. In a PWR nuclear power plant, the number of nuclear safety level units accounts for about 40% of the total number of units, while the cost of a piece of equipment may be increased several times from non-safety level to safety level, so we can see the importance of proper classification. The design of safety function nuclear power plant requires to ensure the safe shutdown of the reactor in any case, to remove heat from the core, and to limit the expected operating events and consequences of accident conditions. The functions necessary to meet these design requirements are called safety functions.


2. Some important tests of class 1E electrical equipment in nuclear power plant


2.1. Electromagnetic compatibility test

The test shall be carried out according to the relevant requirements of IEC 62040-2 UPS EMC standard, emission test ≤ C2, immunity test ≥ C2, and industrial ups.

Among them, immunity includes: 1. Radiation sensitivity test; 2. Power frequency magnetic field radiation sensitivity test; 3. Conduction sensitivity of RF field induction; 4. Immunity of electric fast transient pulse group; 5. Immunity of surge; 6. Immunity of voltage drop and interruption; 7. Induction / contact of power line; 8. Immunity of electrostatic discharge.

The purpose of EMC test is to ensure that the disturbance generated during normal operation of ups will not hinder the normal operation of other equipment. When the disturbance level does not exceed the standard requirements, the UPS equipment can operate normally. In a word, UPS can work normally under severe electrical environment conditions.


2.2 Test on the influence of temperature change on performance

It is mainly the damp heat test under the limit working condition. UPS operates with 100% load, temperature: 49 ℃± 2 ℃. Relative humidity: 95%. Duration: 12 hours. UPS works normally, and the internal limit temperature rise of the equipment does not exceed the specified limit value. In addition, dry heat test, low temperature test and cyclic damp heat test under the condition of limit storage and transportation should be done. The purpose of the test is to ensure that UPS can operate normally under the condition of high temperature and humidity.



3. Mechanical vibration resistance test


Three successive stage tests on each of the three specified shafts.

Stage 1:

Probe for critical frequencies (resonance frequencies or frequencies at which defective operation of the equipment can be observed). Scan the frequency range in full accordance with the test conditions specified below, except that the scanning speed can be reduced in order to determine the key frequency more accurately.


Stage 2:

Durability test with frequency scanning.


Stage 3:

Durability test at fixed frequency. Test each critical frequency that may be found in the initial test phase. If no critical frequency appears at the initial stage, test at a fixed frequency of 100Hz.


Severity

Frequency: 10 to 500 Hz;

Constant displacement (peak value) below transition frequency: 0.075mm;

Constant acceleration above transition frequency: 1.0g;

Test time of sweep frequency durability test: 10 times (each axis);

Test time of constant frequency durability test: 10min (for each shaft).


During and after the test, the prototype (including parts) will not fall, will not have any deformation or damage, will not have any structural failure or tilt that prevents or hinders the implementation of its safety function, and all kinds of switches are on and off normally.


4. Seismic test


The seismic test is an important part of the quality appraisal of the class 1E electrical equipment in nuclear power plant.


4.1 Operation reference earthquake (S1 or OBE) refers to the earthquake that can act on the plant area during the operation life of the identified equipment in the nuclear power plant. The equipment must be designed or operated continuously without improvement.


4.2. The maximum earthquake that may occur during the safe shutdown earthquake (S2 or SSE). Some structures, systems and components are designed to maintain their function under its action.


Using the method of continuous sine wave scanning or self-noise random wave scanning (the selected acceleration level can make the test device get a good signal-to-noise ratio, usually 0.1-0.29). According to the response spectrum of the floor where the equipment is installed, the artificial seismic wave including the response spectrum of the floor is generated as the input signal of the table, and the seismic test is carried out according to the biaxial or triaxial respectively to check its seismic performance. In order to ensure that the envelope of test response spectrum requires response spectrum, 10% margin should be considered in wave making. The purpose of the test is to test the rigidity and strength of the equipment, whether the equipment can work normally under and after the earthquake load, and to perform its safety related functions by simulating the vibration of the seismic vibration table with electrical and instrument equipment.


3.Introduction of class 1E industrial UPS in AVIC-TECH nuclear power plant


3.1 Product introduction

ANP series nuclear power special grade UPS is suitable for providing reliable energy for instrument control, monitoring and other active equipment of nuclear power plant to perform safety functions, and belongs to nuclear power safety related equipment. The core control part of the product adopts pure hardware control circuit design, without any MCU or DSP participation, meeting the high safety requirements of nuclear power. At the same time, through innovative design, all components of nuclear power products can be maintained at the front door and meet the requirements of high seismic level.


3.2 Main features

  • The core control part adopts the pure hardware control circuit design, without any MCU and DSP participation, meeting the high safety requirements of nuclear power;

  • Core power device adopts 4 times of rated value redundancy design to meet the requirements of nuclear power on working environment;

  • Each functional unit of the system is designed with a separate cabinet to meet the different requirements of nuclear island equipment;

  • Innovative structural design to meet the front door maintenance requirements of all components;

  • Strengthen the anti-mechanical vibration design, the whole machine is firm and reliable;

  • Adopt fully enclosed laminated busbar technology, simple and compact structure, beautiful and generous process, reduce peak voltage, etc.


Author of this paper is He Chun, Chief Engineer of AVIC-TECH.



About AVIC-Tech

AVIC-Tech (Xiamen)Electric Power Technology Co.,Ltd is a high-tech enterprise specializing in R&D, manufacture, sales and service of high-end power supply. Our flagship products are industrial UPS (1kVA-800kVA), dynamic voltage restorer (10kVA-2000kVA), and lithium battery system, which are widely used in nuclear power, electric power, petroleum and petrochemical, rail transportation, industrial manufacturing and other fields.

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