terminal junction box

The terminal block is a kind of interface device that connects the construction line and marks the branch line to provide convenient wiring and line checking. In some cases, in order to facilitate construction and debugging, some special and regular installation settings such as short-circuit isolators can be installed in the terminal block

Terminal blocks are a kind of accessory products used to realize electrical connections, which are industrially divided into the category of connectors. With the increasing degree of industrial automation and the increasingly strict and precise requirements of industrial control, the use of terminal blocks is gradually increasing. With the development of the electronics industry, the range of use of terminal blocks is increasing, and there are more and more types.

Scope of application

The terminal box material is made of high-quality cold-rolled steel plate and high-quality stainless steel plate, and the box structure is designed according to outdoor waterproofing, and the protection level can reach IP54 or IP55 according to the different requirements of users. As a result, the terminal box can be adapted to a wide range of different types of climatic conditions and operating environments.

How it works:

The terminal box contains temperature and humidity controllers to stop condensation and preset the temperature. The temperature and humidity controller is composed of a temperature sensor and a condensation sensor, which monitors the temperature and humidity changes in the terminal box at any time, and when the ambient temperature inside the box is lower than the preset temperature or there is condensation to be generated, the controller automatically starts the heater to run and heat to increase the internal ambient temperature of the box and destroy the small environment that produces condensation. When the conditions for condensation in the box disappear or the ambient temperature reaches the preset temperature, the heater will automatically disconnect and stop heating, and the controller will resume the monitoring state.

Accessory functions

The terminal box is also designed to be installed with a single-phase three-hole 220V, 16A power socket and a service light for users to use during daily inspection and maintenance. At the same time, it is also designed and installed with a transfer switch, and the user can arbitrarily switch the manual and automatic control mode of the heater in the box according to the actual operation needs of the site.

The terminal box is the protective trunk line in the building, which can be used in water and gas metal pipelines, heating, refrigeration, and cooling systems, and the metal components of the building are connected to meet the requirements of the specification for anti-electric shock protection appliances with a contact voltage of less than 50V. Terminal boxes are an important part of modern building appliances and are widely used in high-rise buildings.

The terminal box has a good function and function, which can assist the potential connection, and directly connect the two conductive parts with wires for equipotential connection, so that the fault contact voltage is reduced below the contact voltage limit. The terminal box can ensure good service value and contribution in the event of a fault, and remove the hazardous power supply network impedance of the dangerous fault voltage introduced from the outside of the building through various metal pipelines of the electrical line, so that the automatic power supply cut-off time is too long and cannot meet the requirements of electric shock prevention; When meeting the special requirements for anti-electric shock in bathrooms, swimming pools, hospital operating rooms and other places; The same distributor of the TN system supplies two types of electrical equipment, stationary and mobile, and the fixed equipment protects the electrical appliance when the power supply cut-off time cannot meet the requirements of mobile electric shock prevention.

Application range of stainless steel terminal box and its characteristics:

Features introduction

1. This structure is made of steel plate bending and welding. There is a universal movable frame plate in the box, on which the mounting plate can be fixed and adjusted up and down and back and forth, so the installation of components is extremely flexible.

2. There are doors in front and behind the box, which can be installed off the wall and can be maintained at the same time before and after. There is a ¢60 threading hole at the bottom of the box, and there is a sealing rubber ring to seal and insulate. The lower 200mm high base of the box has ventilation holes, which can be installed in wet areas, or the base can be removed and installed directly on the foundation.

Dehumidification measures for outdoor terminal boxes in substations

When the air is humid, especially in the rainy season, the dampness and condensation in the outdoor terminal box can easily lead to a drop in the insulation resistance of the DC secondary circuit to the ground, and in severe cases, the insulation resistance drops to zero, thus forming a DC positive power supply or negative power supply grounding. If the DC two-point grounding is caused, it will cause protection refusal or malfunction, and even damage the equipment, seriously threatening the safe operation of the power grid. The terminal box will rust the terminal screws and connectors, so that the secondary terminal contact is poor, and it will also make the current circuit terminal heat up or even open the circuit, causing protection refusal or misoperation, causing accidents. Poor contact of terminals such as control loops and signal loops will cause abnormal operation of measurement and control and protection devices, and mistransmit signals, resulting in misjudgment and misanalysis by operators.

Analysis of the causes of condensation

Condensation phenomenon refers to the condensation phenomenon of water droplets on the surface of the inner wall of the cabinet when the surface temperature drops below the dew point temperature. Whether condensation occurs depends on the temperature inside the box, the temperature outside the box, the relative humidity, and the dew point temperature. There are mainly the following reasons for condensation in the terminal box.

(1) The humidity in the area is high, the climate and temperature change greatly, the bottom of the terminal box is humid, and some cable trenches even have waterlogging.

(2) Some terminal boxes are in the basement, the humidity is relatively high, and the temperature inside the box, especially the temperature close to the ground, is lower than the ambient temperature.

(3) Some equipment is temporarily shut down, and the small ambient temperature in the terminal box is lower than the surrounding ambient temperature, and condensation is very easy to form on its surface.

Selection of dehumidification options

The outdoor terminal box carries out the following transformation plan on the premise of ensuring that the sealing ring of the box door is normal and the fire sealing measures are intact.

1. Transformation principle

In view of the actual situation such as the failure of the outdoor terminal box heater in the substation and the failure of the temperature and humidity controller, the heater is not put in or the failure of the fault is frequent, and the original internal temperature and humidity controller is removed, and the low-power heater is often put in. In order to minimize the phenomenon of wire burning caused by overheating during the use of the heater, the terminal box and mechanism box should be selected with a power heater of no more than 50 W, and the maximum temperature in the box where the heater is installed should not exceed 50 °C. It is appropriate to have a micro-positive pressure inside and outside the box, and adopt a multi-point dispersion arrangement scheme, and the specific power is determined according to the size of the box, and the power of the heater is not more than 30 W per 0.1m3.

2. Schematic diagram of transformation

The wiring of the terminal box is re-wiring, the original wiring is removed, the lower terminal leads are opened from the empty to the terminal strip, and then the terminal row leads to the heater, and the metal shell of the heater needs to be grounded.

3. Implement transformation

The size of this switch terminal box is about 45cm×70cm×100cm, and the volume is about 0.315m3. The original switch terminal box has a heater with a power of 50 W, and is equipped with an independent heater that is left open, and the temperature and humidity controller automatically control the heater to cast and retreat. According to the principle of transformation, the temperature and humidity controller was removed, and a 20W heater was installed in the original position, and another 20W heater was installed on the wall of the box opposite the original heater. The temperature and humidity of the terminal box after the transformation are tracked for many consecutive days, and the equipment in the box is running well.

Scope of application:

It is mainly used for power plant and substation circuit breakers, voltage transformers, transformers, metering secondary line terminal connections, as well as substation maintenance power supply and power distribution boxes, power control boxes, lighting boxes and terminal boxes in industrial enterprises. Its materials include steel plate and stainless steel, and the protection level is IP54.