Disconnector (Isolating Switch): The Essential Guide for Power Systems

To help keep workers and machines protected, the role of disconnectors can’t be denied. Disconnectors have the ability to cut off electricity flow whenever needed. Unlike circuit breakers, disconnectors disconnect the electricity flow without breaking the circuit. In this blog, we will discuss disconnect switches completely, covering their basic core functions, types, applications, and more. So, keep reading!

Figure no 1 Disconnectors

1) What is a Disconnector

Switch disconnectors are the devices that provide separation from the power supply. By doing so, disconnectors keep equipment boosted and risk-free of electrical hazards. With no risk of current flow, maintenance can be performed with the utmost safety.

As a result of ensuring personnel safety and equipment protection, disconnectors are broadly utilized throughout substations, transmission lines, and industrial systems. Different categories of disconnectors, such as air-break, gas-insulated, and vacuum disconnectors, are available. Also, disconnectors can be operated manually or controlled remotely.

Figure no 2 What is a disconnector

Disconnectors are not designed to guard against overcurrent or short circuits; however, they assist circuit breakers and fuses in creating a dependable power system. Their simple design, reliable construction, and ability to disconnect circuits make them very important in providing safety and flexibility in any electrical system.   

2) Core Functions of a Disconnector

As with isolating switches, disconnectors have important responsibilities in a power system that involve maintaining the electrical safety and operational flexibility of the system. Here are the key functions of an electrical disconnector.

a) Isolation of Electrical Equipment

The primary function of a disconnector is to isolate or remove one section of the electrical system from any incoming current supply. This ensures that the system cannot be turned on in an unintended manner, allowing maintenance or repairs to be conducted safely.

b) Ensuring Worker Safety

Portions of the electrical circuit will be seen separated, allowing maintenance teams to quickly and easily confirm that the power supply to the equipment is turned off, reducing the chance of electric shocks or accidents.

c) Circuit Segmentation

Disconnectors in large-area power systems make it possible to isolate certain areas of the system without disturbing the whole network so that efficient servicing, system changes, and repairs can be performed.

Figure no 3 Core functions of  a disconnector

d) Operational Flexibility

Disconnectors facilitate the partial isolation of various sections of the power grid, allowing for system maintenance, upgrading, inspecting, and even fault recognition to be carried out with ease. Such flexibility boosts the efficiency and dependability of power distribution systems.

e) Load Management

Disconnectors assist in the switching of power loads between different circuits to maximize the stability of the entire power system. This has proven helpful in industrial plants and electric substations where power distribution is required to be managed effectively.

f) Reliability and Simplicity

Disconnectors have a robust structure and contain few moving parts, which makes them highly dependable and easy to maintain. Their simplicity in construction increases reliability and reduces the need for servicing. Disconnect electrical work in conjunction with circuit breakers and fuses to provide enhanced protection to the entire system.

To conclude, the ability of disconnectors to isolate and furnish electrical networks with full protection, combined with their reliability and efficient ease of operation, renders them imperative in power system infrastructure.

3) Key Differences from Circuit Breakers

Both Disconnectors and Circuit Breakers meet the grid’s requirements, but each still brings something unique. Even though both instruments manage electrical systems, there is a vast difference in their purpose, components, and ways of working.

Figure no 4 Disconnector attributes

• Function: A disconnector is used to isolate any electrical equipment by breaking the circuit, which stops current flow. It does not get rid of fault currents. A circuit breaker, on the other hand, aids in finding exposure and halting the current flow on its own so that the system does not get damaged.

• Operation: Disconnectors can be manually operated or motor-operated and must have the circuit turned off before they can be opened. Circuit breakers work on their own and can trip if there is too much current to prevent the hazardous flow.

• Safety Role: Disconnectors aid in the visual assurance of ensured isolation, which guarantees worker safety. Circuit breakers further improve electrical safety by eliminating any damages that a short circuit or power overload can incur.

• Usage In The System: Disconnectors are primarily used for maintenance isolation whilst circuit breakers perform fault protection in addition to automatic power restoration.

• Design Complexity: Disconnectors possess a less complex structure and have fewer parts when compared to other components of the electrical system. Unlike circuit breakers, which have an array of parts needed to better handle fault currents, disconnectors are more intricate and contain relays and protective mechanisms.

Feature	Disconnector (Isolating Switch)	Circuit Breaker
Primary Function	Isolates equipment from the power supply	Interrupts fault currents
Operation	Manual or motor-operated	Automatic tripping on faults
Current Handling	Cannot break load or fault current	Breaks normal and fault currents
Safety Role	Provides visible isolation	Protects against short circuits and overloads
Usage	Used for maintenance isolation	Used for fault protection and system control
Design Complexity	Simple mechanical design	Complex with relays and protective circuits

Disconnectors and Circuit breakers are parts of the power system, therefore, they must work in perfect conjunction with one another. Disconnectors provide sufficient dismounting needed to protect the system and remove the faulty portions, while the Circuit Breaker does the rest needed to protect the system.

4) Types of Disconnectors

Disconnectors come in various types based on structure, insulation, and mounting. Each type is designed for specific applications in power systems.

By Structure

i) Pantograph Disconnector: This type has a compact design and is used for high-voltage substations. It operates with a scissor-like mechanism that provides reliable isolation while occupying little space.

Figure no 5 Pantograph disconnector

ii) Rotating Blade Disconnector: Features a rotating mechanism where a blade moves to open or close the circuit. It is used widely because of its low-maintenance operation and robust construction.

iii) Double-Break Disconnector: It features two break points in the disconnector's circuit, which nullifies the concerns of isolation contention. Such disconnectors are perfect for maintaining voltages since they ensure complete breaks for servicing needs.

By Insulation

i) Air Insulated Disconnector: It employs air to serve as the medium to provide an insulation barrier for the prevention of electrical contact. It is economical and easy to service, which makes it a popular type for outdoor substations. However, it takes a much greater area.

ii) Gas Insulated Disconnector GIS: This disconnector type uses SF6 ( Sulphur Hexafluoride) gas for insulation, thus making the equipment smaller in altering sizes. This is employed where equipment space is limited, like in urban power grids or in enclosed substations.

By Mounting

i) Outdoor Disconnectors: Constructed to withstand adverse environmental elements such as rain, dust, and high or low-temperature extremes. It is applicable in transmission lines as well as substations for the opening and closing of circuits in relation to outdoor power systems.

Figure no 6 Outdoor disconnectors

ii) Indoor Disconnectors: These are mounted within enclosed switch gear or buildings for protective measures against their immediate environment. These are mostly used in industrial plants, commercial centres, and enclosed substations.

Every type of disconnector is chosen considering the needs of the installation site, such as its voltage level, available area, and surrounding conditions. While gas-insulated types are more compact than their air-insulated counterparts, the latter is cheaper and easier to obtain.

In the same sense, outdoor disconnectors are designed to be more rugged, while their indoor counterparts are made for controlled settings. The appropriate disconnector selection guarantees safety and reliability for any given power system.

5) Application of Disconnectors

In power systems, disconnectors enable safe operations to facilitate protection and system management. It is widely implemented across different electrical systems to create an operational safety gap and enhance protection zones. Here are the primary uses of disconnectors:

• Power Transmission Lines: As the name suggests, these disconnectors operate on power transmission lines and within high-voltage substations. During maintenance works in high-voltage zones, electricity is stored within the transformer to prevent the power from entering the specific area and thus protect the operators.

• Electrical Substations: These disconnectors serve to facilitate and enable maintenance operations with transformers and circuit suitcases.

• Industrial Plants: Disconnecting switches are employed in plants and factories to isolate the machines from the control units to ensure safety while the system is being worked on.

• Renewable Energy Systems: Disconnectors are used to isolate inverters, batteries, and transformers for maintenance in solar farms and wind power stations. Doing so guarantees the reliability of operations and avoids safety issues.

• Railway electrification: In electric railways, disconnectors help isolate different sections of the overhead power lines, ensuring that maintenance can be safely performed on the electrical network without disrupting other parts.

• Commercial buildings: Disconnectors are used in large buildings and shopping centers to control power supply. They let the technicians safely and easily carry out modifications, repairs, and even emergency power-off situations.

• Underground power systems: In underground power systems, disconnectors facilitate the isolation of particular cable network portions for effective diagnosis and maintenance. Thus eliminating the need for service interruptions.

In every application, disconnectors provide effortless, effective disconnection to ensure safety measures are observed when working on live electrical systems.

6)  Safety Rules for Operation

The operation of disconnectors must follow certain safety regulations that prevent the possibility of electrical accidents. Given below are a few of the major rules to observe when operating disconnectors:

! Turn off the power first: Always make sure that the circuit in question is deactivated prior to operating a disconnector. Disconnectors are not meant for live currents.

! Wear Proper Safety Gear: Insulating gloves, safety goggles, and protective suits should be worn whenever an electrical apparatus is dealt with to prevent injury through electric shocks or burns.

! Lockout-Tagout (LOTO) Protocol Must Be Used: Prior to any maintenance work being undertaken, lock and tag the disconnector in the open position to safeguard against inadvertent energization during the work.

! Test For Any Remaining Voltage: Prior to coming into contact with any components of a circuit, it is advisable to use a voltage tester to check if a charge remains. Some circuits are capable of retaining a charge even once they have been disconnected.

! Use Caution and Control While Operating: When opening and closing a disconnector, ensure that the mechanical movement of the switch is controlled in order to prevent a sudden increase in electrical energy or movement.

Figure no 7: Use caution while using disconnectors

! Keep the area clear: Be sure that when the disconnector section is being operated, no other unauthorized persons come near. Yes! It is important to note that high-voltage apparatus should be handled only by those who have received specific training.

! Ensure Regular Inspections: Inspect disconnectors for loose parts, breakage, or corrosion. Systematic maintenance safeguards a failure from occurring and guarantees trusted functionality.

Stressing these precautions enables employees to decrease the chances of risks while using power system disconnectors and enhances safety in the workplace.

If you are looking for reliable disconnectors, our trusted solutions at Delixi Electric offer exceptional quality. We design disconnectors with the utmost safety, durability, and efficiency, which guarantees seamless power isolation. Our products perform exceptionally well and are reliable over long periods for substations, industries, and more. You can contact us right now for effective power solutions!

7) FAQ

1. When to Use a Disconnector?

You can use a disconnector to isolate a part or the whole electrical circuit for checking, maintenance, or repair work. Disconnectors make sure that no electric current is accidentally passed through to the part being maintained. It protects the maintenance crew from electric shock and protects the system from damage.

2. What is the difference between a switch and a disconnector?

The disconnector fulfils the function of electrically isolating a part of the circuit to keep it safe from possible electrical interference, while the switch does not. In ordinary operational work, switches enable, and disconnectors disable the equipment.