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Safety and reliability are of primary importance whether you are upgrading a transmission line, building a substation, or running an industrial facility. This is where disconnect switches come into play.
Electrical circuits are equipped with disconnect switches to provide user safety and equipment safety. In this article, we'll explore high-voltage disconnect switch types and how you can choose a reliable one.
A high-voltage disconnect switch (also known as a high-voltage isolator) is a safety device that physically separates a circuit when maintenance or inspection is necessary. They are mounted for easy switching without load conditions.
Unlike circuit breakers, a high-voltage disconnect switch de-energizes a section or the whole circuit so that technicians can operate. It blocks the flow of current where emergency stoppage, switching operations, repair, or maintenance is required.
These switches are fitted in substations, transmission networks, and industrial plants having medium and high voltage. Some of its functions include:
Ensuring workers' safety
Prevent current flow during repair and maintenance.
Providing visual isolation
Providing system reliability through fault isolation.
Simply put, an electrical circuit is incomplete without a disconnect switch.
Current/live part: This is the element of the high-voltage disconnect switch that supports the electrical load.
Contact system: The contact system is a conductive surface that connects or disconnects the electrical circuit.
Supporting and rotating insulators: These insulators reduce current leakage and the occurrence of flashover. They offer electrical isolation of live components and the ground or other parts.
Operating drive and connecting rods: The operating drive is an electric motor used to move the blades and operate the disconnector. The connecting rods are mechanical linkages that transfer movement from the drive to the moving blades.
Base frame: The base frame is the foundation of the disconnector. It is often made of channel steel; thus, it is robust and provides a stable mount for the disconnect switch.
Earthing switches: The earthing switches create a safe path to ground to protect equipment from electrical faults and surges. It is either integrated into the disconnect switch as a single unit.
There are several types of high-voltage disconnect switches. These types are based on environmental conditions, installation location, operating mechanism, and mounting design.
This fuse is a combination of a fuse and a load break switch. During an abnormal current, the fuse shuts down the circuit, and the switch disconnects the circuit.
The switch has a mechanism that allows you to manually shut off the power to the circuit. The fuse has a tiny filament that matches the current rating of the electrical circuit. In this manner, it will be able to conduct the same current that the electrical circuit is intended to conduct. It will melt if the circuit's current becomes higher than the fuse's rating for an extended period.
If you want power to be restored, you'll need to change the fuse. These kinds of fuses are applicable in medium-voltage distribution networks, industrial electrical panels, and backup protection for transformers.
Our 11kV disconnect switch has a solid link for use on line disconnection and sectionalizing purposes.
A coaxial disconnect switch is a device designed to carry low-loss and high-frequency electrical signals. This disconnection switch is required to safeguard the operator against the risks of electricity and to facilitate the functioning of electricity with the use of coaxial cables.
An electrical system running on batteries has a manual disconnect switch. It is operated by hand, using a lever or crank. It prevents the contacts from welding shut and damaging the switch's ability to function. It is easy to operate and requires no external power.
Common applications of these kinds of fuses include smaller substations, industrial plants, and emergency isolation. Its high performance and compact size also make it useful in machines, power distribution, motor control centers, and solar systems.
This is a high-voltage disconnect switch used to isolate the power supply and the wiring system of a home or workplace. This is the first switch after the utility meter and therefore is also referred to as the service disconnect.
This switch may be housed in a separate box or may be the primary circuit breaker on the home main service panel. It is also ideal for a residential building to have a service disconnect on the exterior and a main service panel, having its own circuit breaker inside.
This is a common disconnect switch in high-voltage systems in utilities, commercial buildings, and factories.
This kind of switch combines the functions of two disconnect switches: the manual and electrical disconnect switches. The disconnect switch may be controlled by a hand and an electric motor. The selection of its operating mechanism depends on the operation you want to perform.
This kind of switch is used in transmission substations, smart grids, and high-voltage networks where manual access is dangerous.
The air disconnect switch operates in the air rather than other media. It is also referred to as a gang-operated switch since the three switches it has on each phase are controlled as a unit.
It works by breaking the connection between the transformer and the load. Instead of disconnecting the substation from the incoming line, it breaks the substation transformer's magnetizing current. The magnetizing current is the minimal amount of current flow required to establish the magnetic field in the central transformer.
Thus, before you disconnect the high-voltage side of a substation, you must first disconnect its load side.
This kind of disconnect switch is used in a power plant to prevent power from being sent to the grid when there is an electrical fault. When the applied voltage changes, the disconnect switch will either open or close in a circuit.
This disconnect switch is used on high-resistance circuits without creating overload. It is used in power transmission equipment to allow voltage application for extended periods than is normally possible.
If the current flow in the circuit exceeds its normal range, the circuit breaker will break over to a new voltage level. This disconnect switch does not send voltage until the current flow has dropped below the setpoint.
This type of disconnect switch has two revolving insulators that open and close the contacts in a sideways motion. The insulators are usually mounted on an integrated base frame. It is optimal when you would like to use a low-cost switch or when overhead is limited.
This kind of disconnect switch is used in transmission substations, switchyards, and outdoor installations. It is also customizable, durable, and low-maintenance. It also provides a visual separation in the event of an electrical fault.
This is a major type of disconnect switch covering disconnect switches above 72kV. They are used in extra-high and ultra-high voltage systems. They also find application in electrical and industrial applications where the power source must be disconnected during maintenance, repair or inspection.
They are either air-insulated or gas-insulated with a robust design and high reliability. Their working principle is simple. When the circuit breaker contacts are opened, an arc is formed due to the metal vapor ionization inside the contacts. If left unhandled, things could easily escalate, and systems will be damaged.
The bright side: this switch has an arc extinguishing mechanism. The metal vapor ionization rapidly condenses to restore dielectric strength.
Our High-voltage disconnect switch ensures an electrical circuit is de-energized for repair.
This type of disconnect switch has a voltage range of 3 to 36kV. It can be used as an indoor switchgear or an outdoor switchgear in secondary substations, distribution feeders, and industrial plants.
It is often metal-enclosed with the interrupting medium insulated with oil, air, or vacuum. It is mainly used to cut off the current when it is above the normal range. It is small, economical, and easily combined with load-break functions.
This type is used on a circuit where manual action and disconnect capability are needed. It is used to work with electrified overhead cables and electrical devices. It can be combined with a vertical or center disconnect switch. It is flexible and has key component options to support your project requirements.
The 3-way disconnect switch is also known as a multi-directional switch or 3-position isolator. It is commonly used to control a light fixture from multiple directions in a room, a large hall, a stairway, etc. You can control the light fixture from whichever end of the room you find yourself.
A 3-way disconnect switch is essential in a building with a 3-way switch. It is an adjustable disconnect switch that interrupts the flow of current during maintenance, repair or inspection. It increases the flexibility of the network and reduces the downtime during line transfers.
This is also fitted in ring main units, industrial plants and distribution substations where flexible switching is necessary.
This type of disconnect switch has two moving contacts that open at two ends towards the center. It is used in substations with limited phase space and long overhead lines. Here, the current path rotates horizontally, making a vertical opening of the current line impossible. It provides fast isolation speed and higher arc interruption.
This type of disconnect switch is used to ground the remaining current in a power line after it has been disconnected from the power source. It often has a snap-action closing mechanism to protect linemen when there is abnormal current flow.
Voltage rating and current capacity: The voltage rating of the disconnect switch should match your system voltage. This makes it capable of peak loading and fault conditions.
Application environment: Where will the disconnect switch be applied? Factor in pollution level, installation location, and altitude.
Operation method: Consider the operation method of your disconnect switch, whether manual, motor-controlled, or remote-controlled.
Maintenance and reliability needs: Some disconnect switches require little maintenance; others require high maintenance. You also want to check its availability of spare parts to reduce downtime and improve the reliability of your systems in the event of an electrical fault.
Space constraints: Consider if you'll need vertical or horizontal clearance, and get a disconnect switch that can fit into that setting.
A circuit breaker protects a circuit by detecting overcurrent or short circuits and then interrupting current flow. A disconnector switch usually has a visual indication but is incapable of interrupting live currents.
The maximum distance should not be more than 50 feet from the equipment it controls or protects. This ensures that it is ‘within sight' for safe and immediate operation during servicing, maintenance, repair, or other emergencies.
A service can have only one main disconnect. There are, however, instances where two or more disconnectors are permitted to be used, though certain configurations must be met.
An isolator switch is any form of manually operated switch that breaks an electrical circuit to allow safe maintenance, inspection, or repair. It is not an overcurrent guard, but an off-load guard.
A disconnecting switch in a substation cuts off a section of the electrical system, such as a transmission line, so that it can be visibly isolated during maintenance or repair.
The safety and reliability of an electrical installation largely depend on high-voltage disconnect switches. With various types and designs available, each one can fit into your project needs, as long as you choose the right one.
Haivol Electrical is a manufacturer of high-voltage disconnect switches, committed to assisting you in identifying the ideal solution to your application. Contact us now for further enquiries.
