General: Fire safety technology (14) Power supply and distribution of electrical equipment for fire fighting and electrical fire and explosion protection

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The first section   Fire-fighting electricity supply and distribution system

First, the power distribution system settings

The power supply and distribution system for fire-fighting equipment should be set up as a stand-alone system. When there is a substation in a building, it is necessary to start a self-contained system at the substation. When the building is under low-voltage line, it must start its own system at the entrance.

(I) Inspection of distribution equipment

The power distribution equipment for fire-fighting electrical equipment shall be installed at the incoming line of the building or at the distribution transformer station. The emergency power distribution equipment shall be set separately from the main power distribution equipment; if it is limited by geographical area, it cannot be set separately. When it is necessary to arrange in parallel, a fireproof partition must be installed at its boundary.

(b) Starting device inspection

When the fire-fighting electricity load is one class, an automatic starting device shall be provided and the power shall be supplied within 30 seconds after the main power supply is cut off . When the fire-fighting load is two-stage and the automatic starting mode is difficult, a manual starting device may be used.

(C) automatic switching function check

The two power supply circuits for fire-fighting electrical equipment such as fire pumps, fire lifts, smoke protection and smoke extraction fans shall be automatically switched at the last level distribution box. The control circuit of fire-fighting equipment must not use frequency converter as a control device.

Except fire-fighting water pump, fire-fighting elevator, smoke-proof and smoke-exhausting fan and other fire-fighting electricity equipment, other fire-fighting electricity equipment in each fire-proof zone shall be powered by double power supply or double-circuit power line in the fire-fighting power supply. The power supply will be automatically switched over and the distribution box will be installed in the fire district where it is located. The distribution box will then be assigned to the appropriate fire fighting equipment. For the fire fighting equipment with the same function, the same nature and small capacity, it can be regarded as a group of equipment and a branch circuit is used for power supply. The equipment for each branch circuit should not exceed 5 units, and the total design capacity should not exceed 10KW .

Section II   Electrical fire protection and explosion protection requirements and technical measures

First, the fire inspection content

(a) Plane layout

The distance of outdoor conversion and distribution equipment from storage yards, flammable liquid storage tanks, and warehouses of Class A and Class B plants shall not be less than 25m ; it shall not be less than 10m away from other buildings ; the distance from liquefied petroleum gas tanks shall not be less than 35m ; changes in petrochemical plants The power distribution room should also be located on one side of the installation and outside the explosion danger zone. The greater the amount of transformer oil, the lower the fire resistance rating of buildings and the greater the storage of dangerous goods, the greater the required spacing, and firewalls may be added if necessary.

Indoor voltage of 10kV or more, 60kg or less total oil is oil-filled equipment, can be installed in both sides of a separator intervals; a total of 60 ~ 600kg oil, should be installed in the partition wall intervals of explosion; If the total oil is more than 600kg , it should be installed in a separate explosion-proof interval. 10kV and below, change, distribution room should not be located directly above or below the explosion hazard environment. Substations are adjacent to explosion hazardous environments at all levels, and at most only two walls connected to one another can be shared with hazardous environments.

(b) Environment

1. Elimination or reduction of explosive mixtures

The production equipment, storage containers, pipe joints and valves with inflammable and explosive substances shall be strictly sealed and inspected and inspected frequently.

2. Elimination of ignition

Electrical equipment and devices that can generate sparks, arcs, and high-temperature hazards during operation should not be placed in flammable and explosive hazardous locations. Electrical equipment and devices installed in flammable and explosive locations should be sealed explosion-proof electrical appliances, and portable electrical equipment should be avoided as far as possible.

(c) Protection

Metal enclosures of electrical equipment in explosion and fire hazard locations should be reliably grounded (or connected to zero).

Second, the inspection of fire prevention measures

(I) Inspection of Fire Protection Measures of Transformers and Distribution Equipment

1. Transformer protection

The transformer should be equipped with a short-circuit protection device. When an accident occurs, the power supply can be cut off in time.

In addition, the high-voltage side of the transformer can also be used for short-circuit protection and overload protection through the use of over-current relays. According to transformer operation conditions, capacity, voltage level, gas protection, differential protection, temperature protection, low voltage protection, over voltage protection and other facilities should also be provided.

2. Prevent lightning strikes

In order to prevent lightning strikes, lightning arresters should be installed on the overhead side of the transformer to introduce the power supply side and have a certain protection gap.

3. Grounding measures

In a low-voltage power distribution system with a well grounded neutral point, a protective zero-crossing method should be used. However, the urban public power grid should adopt a unified protection method; in order to avoid accidents caused by the combination of zero protection and ground protection, all rural distribution networks must not implement protection zero, but should adopt a protective grounding method.

In a low-voltage distribution network that is not grounded at the neutral point, protective grounding is used. High-voltage electrical equipment is generally protected by grounding.

4. Overcurrent protection measures

Circuit breakers, fuses, and similar overcurrent protection devices should be installed in the circuit to prevent electrical overload caused by disasters. The setting parameters of protective appliances shall meet the following requirements:

( 1 ) The rated current or setting current of the protective appliance shall not be less than the calculated load current of the loop;

( 2 ) The rated current or setting current of the protective appliance shall not be greater than the allowable continuous ampacity of the circuit;

( 3 ) The current for ensuring the effective operation of the protective device should not be greater than 1.45 times the circuit ampacity .

5. Short-circuit protection measures

6. Leakage protection appliances

( 1 ) When installing a leakage protector with short-circuit protection, it must be ensured that there is a sufficient arcing distance in the arc discharge direction.

(B) Inspection of fire protection measures for low voltage distribution and control appliances

Low voltage power distribution and control wire insulation should be no electrical aging, corrosion and damage phenomena; on the same wire connection terminals are not more than two, and the same two wire diameter, complete lock washers and other components; 1101.11 feed is correct; The connection shall be made of copper or bolts and screws with electroplated metal layers for rust prevention. The connections shall be firm and there shall be anti-loosening devices. The electrical connections shall be free of traces of overheating, rust, burns, welds, etc. Zero ( PEN ) or ground ( PE ), reliable connection; sleeve, porcelain exterior without damage, crack marks.

Low voltage distribution and control electrical installation area, no leakage phenomenon. Arc extinguishing devices for low voltage distribution and control appliances shall be intact. Insulated wires connected to heating elements (such as tubular resistors) should be insulated. The fuses should use standard melts as required. When the electric appliance is near a high temperature object or is installed on a flammable structure, heat insulation and heat dissipation measures should be taken. The electrical insulation resistance between the phases should not be less than 5M Ω.

1. The knife switch

Reduce contact resistance to prevent overheating. Contacts are made of materials with low resistivity and compressive strength.

2. Combination switch

The control switch and fuse that can cut off the three-phase power supply should be installed on the switch.

3. Circuit breaker

During use, components such as the transmission mechanism, arc extinguishing chamber, contacts, and phase-to-phase insulation spindle should be inspected periodically. If activities such as malfunction, damage, deformation, corrosion, overheating, or abnormal sound are detected, they should be dealt with promptly. Check whether the working position of the arc extinguishing cover is moving, whether it is complete, whether it is damp, and so on. For circuit breakers with electric closing, check that the closing solenoid mechanism is in normal condition.

4. Contactor

In view of the frequent separation and contact characteristics of the contactor, the contactor shall be checked and repaired once a month. The contacts shall be fastened and the damaged parts shall be promptly replaced. The anti-rust oil on the pole face shall be wiped clean to prevent grease sticking. Causes the contactor not to release after power off.

5. Starter

6. Relay

Since the control relays operate very frequently, it must be done at least twice a month.

(c) Inspection of fire protection measures for electrical lines

1. Measures to prevent short circuits in electrical lines

Circuit breakers or fuses shall be installed as required on the line so that the power can be cut off in a timely and reliable manner in the event of a short circuit on the line.

2. Measures to prevent overloading of electrical lines

3. Measures to prevent excessive contact resistance of electrical lines

4. Installation requirements for indoor wiring

When designing and installing circuit in the house, the type of the conductor must be properly selected according to the environmental characteristics of the electrical equipment used. The insulated conductor should be protected against damage due to damage caused by the insulation. During use, it must be checked and repaired frequently; when wiring, between the conductor and the conductor The distance between the fixed points of the wire and the wire shall be maintained. In order to prevent mechanical damage, when the insulated wire passes through the wall or the flammable building components, it shall pass through the insulating tube built in the wall. Each tube should only wear one wire. The distance between the outlet ends of the insulating tube ( porcelain tube ) protruding from the wall should not be less than 10mm .

(four) socket and lighting switch

When direct, alternating current or plugs of different voltage levels are installed in the same place, there should be obvious differences. Different structures, different specifications and non-interchangeable sockets should be selected. The matching plugs should be used in accordance with DC, AC and different voltage levels. . The floor outlet panel should be solid, reliable and sealed. Single-phase two-hole socket, the right hole or upper hole facing the socket is connected with the phase line, the left hole or the lower hole is connected with the zero line; the three-hole socket is connected with the right hole of the socket and the phase line, the left hole and the zero line connection. In the wet place, the socket shall be a protected type with a sealed ground contact with a protective earth conductor. The installation height shall not be less than 1.5m .

The connection between the wire and the socket or switch shall be firm and reliable. The screw shall be pressed tightly without looseness and no looseness or damage to the panel. In places where Class I appliances are used, a power outlet with a protective wire contact must be provided and this contact must be connected to the protective ground ( PE wire) as an electrical path. The installation height of sockets in workshops and test rooms shall not be less than 0.3m from the ground ; the installation height of sockets concealed in special places shall not be less than 0.15m from the ground ; the installation height of the same indoor socket shall be the same. The socket panel should have no ablation, discoloration, or melting traces.

Non-temporary use of electricity, should not use mobile sockets. When using a mobile socket, the power cord must be copper core cable or sheathed cord; it must have a protective grounding wire ( PE wire); it must not be placed on combustibles; it must not be used in series; it must not be used in excess capacity.

(five) household appliances

Electric appliances such as refrigerators and televisions shall not be continuously switched off and powered on in a short time; the rear of the refrigerator shall be kept dry and ventilated, and no combustibles shall be placed behind the refrigerator.

The TV should ensure good ventilation. If it is not used for a long time, especially in the rainy season, it should be used for a few hours at regular intervals. The heat emitted by the TV itself should be used to dissipate the moisture in the machine; the outdoor antenna or the lightning arrester for the shared antenna should have good Grounding, try not to use outdoor antennas during thunderstorms; use electric blankets for the first time or after long-term shelving, should be energized for 1 hour before being monitored by someone to check the safety; fold the electric blankets not to fix the position; do not On the sofa, Simmons and the wire bed, a linear electric blanket is used. This electric blanket should only be used on a wooden bed; avoid contact between the electric blanket and the human body, and do not lay a layer of sheets on the electric blanket to prevent the body from rubbing. The electric blankets were pleated, causing local overheating or damage to the electric wires and accidents.

The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.

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