Reasonable application of relay

I. Overview <br> <br> system development, pay close attention to the designer and must give priority to solve a practical problem: two high-voltage switchgear systems used by numerous relays, auxiliary multi-touch switches, limit switches and pressure Components such as switches, which account for about 70% of the proportion of relays, face a variety of complex relay products, how to properly select, correct application, especially as a secondary control part of the high-voltage switchgear, the use of a large number of relays, In the operation, it also has its own unique characteristics. The quality of the selection is directly related to the reliable and safe operation of the substation equipment. In the event of an accident, it will be particularly serious. Therefore, to make a reasonable choice and apply it correctly, it is necessary to fully study the analysis system. The actual application conditions and actual technical parameters require that the technical performance that must be achieved for the selected relay products must be appropriately presented. In the design of the entire system, the importance of the entire system, the degree of reliability, the environmental conditions used, and the costs are taken into account. Comprehensive consideration of factors to choose a reasonable successor Device.

Second, the selection of the environmental conditions <br> <br> climatic stress factors, mainly refers to the temperature, humidity, atmospheric pressure (altitude), coastal atmosphere (salt spray), dust pollution, chemical gases and electromagnetic interference Factors such as taking into account the high-voltage switch operating in many bad conditions, especially as open-type high-voltage circuit breaker equipment running in the outdoor environment, working conditions are worse, and the long-term reliability of the special operation and the key parts of the system must use high altitude, The fully sealed product with strong electrical resistance, because only the fully sealed relay can have excellent long-term resistance to harsh environmental performance, good electrical contact stability, and reliable switching load capability.

1. The influence of temperature on the relay The relay is a heat-sensitive component. High temperatures can accelerate the aging of the internal plastic and insulating materials of the relay. The contacts are oxidized and arc extinguishing difficult. The technical parameters of the electronic components decay, and the reliability is reduced. Because the high voltage switch is internally installed The flooding and thermal insulation heaters, therefore, must not be placed close to flooding and thermal insulation heaters throughout the design of the system, and should maintain good ventilation conditions. Although the relay is afraid of heat components, but too low temperature can not be ignored, low temperature can make contact cold viscous effect, contact surface exposed, many manufacturers of relays indicate the minimum temperature of a 25 °C, but the high voltage switch is applied in the alpine There are also not many regions. Therefore, it is recommended that there be enough room for selection to avoid relays being unreliable due to low temperatures. Under proper conditions, heaters are added in high-cold areas to ensure reliable operation of the relays at low temperatures and ensure stable operation of the entire system.

2. The influence of low pressure on the relay Under the condition of low pressure, the heat dissipation condition of the relay deteriorates, and the temperature of the coil increases, which changes the relay's given pull-in and release parameters and affects the normal operation of the relay. The low pressure can also insulate the relay. The resistance is reduced, the arc extinguishing of the contacts is difficult, and the contacts are easily melted, which affects the reliability of the relay. For low pressure conditions, the method of sealing the entire machine is recommended.

3. The influence of mechanical stress on relays mainly refers to the effects of stress, vibration, impact, and other stress factors on the anti-earthquake stress and anti-mechanical stress of the control system. The vibration caused by the circuit breaker's self-vibration and the closing and closing operations in the high-voltage switch have more effect on the relay. Large, you should choose the middle armature relay balance mechanism, for the electromagnetic relay reed suspension structure, low natural frequency, oscillation and shock can cause resonance, resulting in relay contact pressure drop, prone to momentary disconnection or contact jitter , affect the reliability of the relay, it is recommended in the design as much as possible to use anti-vibration measures to prevent resonance.

4. Influence of insulation voltage on the relay The exposed insulator of the non-sealed or sealed relay is exposed to dust, water and gas pollution for a long period of time, resulting in a decrease in its dielectric strength and failure of insulation breakdown. Therefore, the following points should be noted:

4.1 sufficient creepage distance: general requirements of not less than 3mm;

4.2 sufficient insulation strength: between the conductors without electrical contact is greater than AC2000V, the contact between the same group is greater than AC1000V. (3) The ability to withstand weather stress for a long time: The coil is resistant to mold, and the insulation resistance level is stable and reliable for a long time.

5. The influence of the contact output (switching circuit) load mainly refers to the contact load characteristics, such as: lamp load, motor load, inductor, contactor (relay) coil, resistive load, etc.; contact load value (open circuit voltage Values, closed-circuit current magnitude, such as: low-level load, dry circuit load, low current load, large current load, etc.

Any automation equipment must really determine the nature of the load and the amount of load that are actually required. It is especially important to use suitable relay products. The failure or reliability of the relay is not reliable, mainly refers to whether the contact can complete the specified switching circuit function. If the actual load of the switch is inconsistent with the switching load specified by the selected relay, the reliability will not be discussed.