1 The impact of external interference on electric perimeter fences

There are 2 types of small animals. One type is birds. Due to the suspended state of birds falling on electric perimeter fences, they will not cause voltage leakage and therefore will not trigger an alarm. Another type is animal. When the paws of small dogs and other animals touch the fence, they will experience an electric shock due to the generated voltage difference, causing the small animals to flee in pain. Due to the alarm delay setting on the electric perimeter fence host, it usually takes 3 seconds for the alarm to trigger. This situation will be filtered out and no false alarms will be generated. This alarm delay parameter can be set, ranging from instant alarm to 5-second delay alarm, and can be flexibly selected. The normal working voltage on the fence is 700-900V or 4000-8000V, while the default alarm voltage detected by the electric perimeter fence host is 750V or 5000V. When the electric perimeter fence is affected by external factors and causes voltage leakage below the 5000V alarm line, an alarm output will be generated. If the leakage exceeds 5000V, no alarm will be triggered. So general small animals, green trees and other external disturbances will not cause false alarms when the alarm line is 5000V.

The impact of weather on electric perimeter fences: If it is due to weather conditions, especially extreme weather conditions, we can adjust the alarm voltage to reduce false alarms.

2 The security of electric perimeter fences

(1) From a technical perspective

Although the voltage of the electric perimeter fence ranges is from 5000V to 8000V, it has a strong deterrent effect on intruders. However, whether it can cause damage to intruders depends on the current and pulse power. Generally speaking, the single pulse power of traditional prison high-voltage power grids is 40 millicoulombs, while the single pulse power of electric perimeter fences is only 2.5 millicoulombs, a difference of nearly 20 times. At the same time, the pulse current of the electric perimeter fence has a peak value of 300 milliamps in a one second pulse cycle, with a duration of only 1.5 milliseconds, which is very short. The current of traditional high-voltage power grids is above 10 amperes. So, in terms of a single pulse, the energy of an electric perimeter fence can only achieve a sense of deterrence, not harm, and is safe. At the same time, if someone crawls on the electric perimeter fence due to excessive tension, it will cause a short circuit in the electric perimeter fence. At this time, if the traditional high-voltage power grid sticks to the intruder, it will cause continuous damage to the intruder, and the electric perimeter fence will issue an alarm within 1 second. At the same time, the voltage of the electric perimeter fence will become 0, and the electric perimeter fence host will stop voltage output, which will not cause continuous damage to the intruder. At the same time, electric pulse detectors have two output modes: high voltage and low voltage. High voltage has a sense of electric shock, while low voltage does not have a sense of electric shock deterrence. Both modes can trigger an alarm. If you are concerned about accidental injury caused by high voltage mode, you can choose low voltage mode, which is the safest option at this time.

(2) How to link with the burglar alarm system

When the electric perimeter fence host alarms, it outputs a pure on-off signal, which can be directly connected to various burglar alarm control panels in the security industry to achieve alarm linkage. It can also be linked to other security alarm systems such as video surveillance systems. The electric perimeter fence is equipped with multiple burglar alarm devices, which can form a complete perimeter security system through the supporting equipment, meeting the needs of different users with different security levels.

3 Wiring technology for electric perimeter fences

(1) A defense zone is a series connection loop from the transmitting part to the front fence, and then to the receiving part, which must be connected in series, not in parallel, and not branched.

(2) High voltage resistant wires must be used to connect wires crossing intersections to avoid conductivity or short circuits.

(3) There must be sufficient space gap between wires and between wires and metal conductors.

(4) The electric perimeter fence system should have a good grounding system, and the grounding point should be separated from the grounding point of the power line. The grounding resistance should be less than 4 ohms.

(5) There are two ways to connect alloy wires.

• The first method is to use self-winding method to connect, and the joint should be tightly wound, not less than five times.
• The second method is to connect with a wire connector. First, insert the two wire ends that need to be connected into the connector, and then use pliers to press the wires tightly into the connector. Since the crimping may not be very tight and may become loose, it is necessary to wrap the two heads separately around their own wires. The winding must be tightly attached to the alloy wire being wound, and the number of winding turns should not be less than 5.

(6) Different metal wires should be avoided. Because metals of different properties are connected together, electrochemical reactions can cause corrosion, so the material of the core and alloy wire of high-voltage insulated wires must be the same material.

4 Installation techniques for electric perimeter fences in special locations

(1) How to install the door of an electric perimeter fence

In the electric perimeter fence system, the door is the weakest link because it is a frequently moving object. The design of the door should pay attention to the electrical contact between the wires and the door frame itself, and should be designed to not affect the movement of the door hinge.

(2) How to lay wiring for underground installation

When electric perimeter fences need to be wired underground, high-voltage insulated wires with a rated voltage of 15KV should be selected and threaded into insulated conduit. The wire with positive pole and the wire with negative pole are respectively threaded into different insulation tubes. High voltage insulated wires should avoid joints as much as possible. Because the underground is usually damp, it is difficult to maintain good insulation strength at the joints. If the joint cannot be avoided, the insulation of the joint part should be strengthened. For example, using silicone rubber encapsulation or turning the joint above the ground.

5 Distinguishing between electric perimeter fence fault alarm and intrusion alarm

(1) When the main power supply loses power, the electric perimeter fence host automatically switches to the battery working state, and there will be a fault alarm output without intrusion alarm. When there is a protective relay at the alarm output terminal, security personnel are required to reset the electric perimeter fence host on site within 48 hours (disarming and re-arming). After resetting, the fault alarm will be automatically cleared.

(2) When the main power supply is restored and the battery quality is intact (within one year of use), the electric perimeter fence system switches to the main power supply state, and the battery automatically charges without any fault or intrusion alarms.

(3) The independent working time of the electric perimeter fence host battery is about 4 hours. If the battery power consumption exceeds 4 hours (when the battery voltage is below 11V), if the main power supply is not restored at this time, the entire electric perimeter fence system will be paralyzed due to power outage, and there will be fault alarm and intrusion alarm outputs.

(4) The general lifespan of a battery is about 1 year, and it will be scrapped after 1 year.

(5) When the electric perimeter fence host is in the disarmed state, the battery inside the electric perimeter fence host is supplying power normally. At this time, only the chip inside the electric perimeter fence host consumes power, and the power consumption is negligible compared to the storage capacity of the 4AH12V battery.

(6) When the electric perimeter fence host is in a power-off state, that is, there is no battery power supply or main power supply in the electric perimeter fence host, the relay in the electric perimeter fence host is in a closed state, which means there is an intrusion alarm and fault alarm output.