Portable grounding up to 1000V: requirements, designs and connection rules

Grounding is essential to protect against electric shock. The earth is used in this case as a conductor to reduce the impact of voltage on humans. Portable grounding up to 1000 V is also a mobile protective device when working in the area of ​​electrical networks. It is used during work where there is no stationary grounding.

Requirements for mobile devices

First of all, mobile protective devices must be thermally and dynamically short-circuit-proof. As a result of a short circuit, the temperature of the wires rises sharply, so the ground sections must withstand strong heating. It is also worth noting the following requirements for portable grounding:

1. The strength of the connecting mechanisms fixed on the current-carrying wires should prevent their mechanical breakdown.
2. Contacts must be strong and reliable to prevent overheating and, in some cases, breaking.
3. The grounding conductors must prevent the appearance of the operating voltage of the electrical installation as a result of a break at the ends.
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In addition, the necessary requirements for the minimum thickness of the wires of the mobile protection device have been adopted. So, to service electrical equipment with a voltage above 1000 V, the cross-section must be at least 25 mm², and up to 1000 V - 16 mm².

When portable grounding 10 kV is used, the wire thickness should be between 120 and 185 mm². Since it is very difficult to work with such wires, it is allowed to use two protective devices connected in parallel.

In electrical networks with a protected neutral wire, the thickness of the conductors is determined by the magnitude of the short-circuit current in a single-phase circuit. In networks with isolated neutral grounding must provide thermal stability with a two-phase short circuit.

Grounding design

For the manufacture of grounding, only uninsulated wires are allowed. This is done in order to detect damaged cores in time, as this reduces the design cross-section and can lead to a wire breakage by a short-circuit current.

Usually, copper cables are used in their capacity, which are attached with clamps to the handles with insulation for phase bridging and connection to the grounding bus. All connections are made without the use of lugs to prevent contact failure.

Structures made of four earthing switches are designed to work with three-phase electrical devices. In this case, the contact of the wires in the three-phase grounding with each other and directly with the conductor connected to the ground is carried out firmly and reliably.

For this, special equipment and welding are used. The use of a bolted connection is allowed, but it must be soldered. The use of one solder is not allowedas it will melt at a high short-circuit temperature.

Manufactured equipment

Currently, quite a few brands of portable grounding are produced. They are designed to work with overhead lines and distribution systems. Among them, the following are worth noting:

1. ZPL - portable equipment for working with overhead lines from 0.4 to 220 kV. Devices with wire cross-section from 16 to 95 mm² and non-removable rods are produced under this brand.
2. ZPL-1 SIP is a protection device for the safe maintenance of overhead lines up to 1000 V, equipped with self-supporting insulated wires. It is connected to the line through a special adapter.
3. ZPP - a number of protective devices designed to operate in switchgears with voltages from 0.4 to 220 kV. The kit includes phase clamps and grounding clamps.
4. KShZ 6-10 is a device that protects during work on overhead lines with voltages from 6 to 10 kV. It consists of two telescopic rods with a maximum length of 320 cm. The wire cross-section is 25 mm².

It is also worth noting the following devices: a protective device for fire nozzles ZPS, devices for protecting fire engines ZPPM, mobile grounding for a lightning cable overhead lines ZPGZ, etc.

Installation rules

The use of mobile devices with conductors not intended for protective work is not allowed. Do not connect by twisting wires. Protection devices are installed on all sides, from where voltage can be supplied to the disconnected section.

Even if in the process of work part of the section is turned off with the help of a switch, a protective device is still installed on each disconnected section. All operations are carried out by means of a rod, which is integral with the protective device.

With its help, all the phase clamps are installed in turn. First, the ground is connected to appropriate wiring or special construction. After checking for the presence of voltage, the remaining terminals are connected.

If the design of the boom does not allow the installation of the clamps, then it is done manually using special gloves. In switchgears, fastening work begins from the very bottom, that is, from the floor or ground, avoiding areas that have not yet been protected.

In these cases, it is possible to climb any equipment only after a complete check of the absence of voltage. It should be borne in mind that there is no voltage on live parts only when ground is connected to them. Therefore, after removing the protection, it is forbidden to touch live parts.