Circuit breakers will always trip the circuit when it will open contacts of the breaker and cannot be visible physically from outside of the breaker, that is why it is recommended not to touch any electrical circuit just by switching off the circuit breaker in the bay. There must be some arrangement then only we can see the open condition of the section of the circuit before touching it in the isolator. The isolator is a mechanical switch that isolates a part of the circuit from the system as when required from the device. Electrical isolators separate from rest for safe maintenance works. So the isolator is a manually operated mechanical switch that will separate a part of the electrical power. Isolators are used to open a circuit under no load in the system. And the main purpose is to isolate the circuit from the other and is not intended to be opened while current is flowing in the line. Isolators are generally used for breaker so that repair or replacement of a circuit breaker can be done without any danger of the system.
There are different types of isolators available depending upon system requirement of system such as
Double Break Isolator
Single Break Isolator
Pantograph type Isolator.
Depending upon the position in the power system, the isolators can be seen in the
Bus side isolator – the isolator is directly connected with the main bus
Lineside isolator – the isolator is situated at the line side of any feeder
Transfer bus side isolator – the isolator is directly connected with the transfer bus.
Let’s discuss the constructional features of Double Break Isolators. The central post insulator carries a tubular the flat male contact which is used to rotate the horizontally with a rotation of central post insulators in the range of the system the region.
The female type of contacts is fixed on the top of the other post insulators which will be fitted at both sides of the central post insulator in the form of the system. The rotational movement of male contact causes to come itself into female contacts and isolators become closed. The rotation of male contact in the opposite direction makes it out from female contacts and isolators become open.
Rotation of the central post insulator is done by a driving lever which will be the mechanism at the base of the post insulator, and it is connected to the operating handle of the motor (in case of motorized operation) and the isolator through a mechanical tie rod of the system.
The contact arm is divided into two parts one carries male contact and the other carries female contact. The contact arm moves due to the rotation of the post insulator upon which the contact arms are fitted. Rotation of both post insulators stacks in opposite to each other causes to close the isolator by closing the contact arm of the system. Counter rotation of both post insulators stacks open the contact arm and the isolator becomes in off condition. This motorized form of this type of isolator is generally used, but an emergency hand driven mechanism is also provided.
Earthing switches are mounted on the base of the line side isolator. Earthing switches are usually vertically broken switches. Earthing arms are commonly used for (contact arm of the earthing switch) which is usually need to aligned horizontally at off condition during switching on the operation, these earthing arms rotate and move to a vertical position and it will make a contact with earth female contacts and that is fitted for the top of the post insulator stack of the isolator at its outgoing side of the system. The earthing arms are so interlocked with the main isolator moving contacts that it can be closed only when the primary contacts of the isolator are in the open position. Similarly, the main isolator contacts can be closed only when the earthing arms are in the open position
Operation of Electrical Isolator
As no arc quenching technique is provided in isolator it must be operated when there is no chance current flowing through the circuit in the system. No live circuit should be closed by the isolator operation n the system. A complete live closed-circuit must not to be opened by the isolator operation, it will be closed and completed by isolator operation to avoid huge arcing in between isolator contacts system. That is why isolators must be open after the circuit breaker is open, and these must be closed before the circuit breaker is closed. The isolator can be operated by hand locally as well as by motorized mechanisms from a remote position in the system. Motorized operation arrangement costs more compared to hand operation and we need to make decisions that must be taken before choosing an isolator for the system and in other hand-operated or motor operated economically optimum for the system in the region. For voltages, up to 145 VK system hand operated isolators and is used for the higher voltage systems like 245 VK or 420 VK and above motorized isolators are used by the high voltage.
The isolator is one type of switching device circuit that is totally not triggered in order to perform the preservation. These are also recognizable like isolation switches to isolate the circuits of the system. These switches are applicable in industrial, distribution of electrical power if the voltage, etc. High voltage type isolation switches are utilized in substations for permitting isolation of equipment like transformers, circuit breakers in the system. Usually, the disconnector switch is not proposed for circuit control but it is for isolation in the system. Isolators are activated either automatically or manually operated by the system.
The isolator can be defined as; it is one type of mechanical switch fraction of the electrical circuit when it is required of the system. Isolator switches are used for opening an electrical circuit in the no-load condition of the system.
The electrical isolators are classified based on the requirement of the system which includes the following on the system.
Double Break Type Isolator
Single Break Type Isolator
Pantograph Type Isolator
Double Break Type Isolator
This type of isolator consists of three loads of post insulators in the system. The middle insulator holds a flat male or tubular contact that can be turned in the form of a middle post insulator. The rotation of the middle post insulator can be done by a lever of the method at the bottom of the post insulator, and also it will be related to manual operation (operating handle) or motorized operation motor (using motor) of the isolator via a mechanical knot rod of the system.
Single Break Type Isolators
In this type of isolator, arm contact is separated into two elements of the system. The first arm contact holds male contact, as well as second arm contact, holds female contact in the isolator. The arm contact shifts because of the post insulator rotation upon which the arm contacts are fixed in the range.
The post insulators rotation stacks in reverse to each other which makes to shut the isolator by shutting the arm contact of the system. Post insulators counter-rotation stacks to open the arm contact, as well as an isolator, rotate into an off condition in the system. Generally, the motor-operated isolator is used however an emergency manual operated isolator is also offered to the system.
The pantograph type isolator permits the current switchgear installation, and it requires the least space of the system. This type of insulator includes a post insulator as well as an operating insulator in the isolator.
According to the power system location, we need to classified into three types such as Bus Side Isolator is a type of Isolator that connects by the major bus of the system.
Line Side Isolator stay connected by a feeder inline side.
Transfer Bus Side Isolator stay connected by the major bus of a transformer Electrical Isolator Operation
The operation of an electrical isolator can be done by the following two operational methods namely opening and closing.
Opening Operation of Electrical Isolator
In the beginning, open the major circuit breaker. Then divide the load from a system with isolator opening of the system Close the earth switch. Earth switch can become an interlock system with an isolator. That’s means when the isolator is open only that time earth switch can be closed.
Closing Operation of Electrical Isolator
Detach the earth switch.
Shut the isolator.
Shut the circuit breaker.
Difference between Isolator and Circuit Breaker
The main difference among the isolator as well as the circuit breaker is that the isolator detaches the circuit at the OFF-load situation while the circuit breaker detaches the circuit at the ON-load situation of the system of the system.
But these two have a similar principle like disconnection for isolating the parts of the electrical circuit form the system. This cannot function in an on-load situation where there is any fault occurs in the system then the circuit breaker will trip routinely in the isolator.
The main differences between these two are discussed below.
Type of Device
An isolator is an off-load apparatus whereas the circuit breaker is an ON-load apparatus.
The operation of the isolator is manual whereas the operation of the circuit breaker is automatic.
The isolator is one type of mechanical apparatus that works like a switch whereas circuit breaker is an electronic apparatus made with BJT or MOSFET.
When a fault occurs in a substation, then isolator cuts out a portion of a substation. The other apparatus works without any intrusion.
The circuit breaker is like an MCB or ACB that trips the complete system if there is an error occurs
Isolators have a small withstand capacity when contrasted to Circuit Breaker.
Circuit breakers have a high withstand capacity at the condition of ON-load.
An insulator is one type of detaching switch which works under the condition of off-loading in the region. It separates the circuit part in which the error takes place from the power supply of the range. Isolators are applicable for high voltage devices like transformers of the system. The main function of Isolator is, it blocks the DC signals & allows the AC signals to flow to the system.
Circuit Breaker is one kind of protection device which works like a switch to the system. When the fault happens in the system, it opens as well as closes the circuit contact in the range. It separates the circuit automatically when a short circuit or overload takes place of the system.
Applications of Isolator
The applications of the isolator include the following range.
The applications of Isolators involve in high voltage devices such as transformers in the system. These are protected with a locking system on the external or with a lock to stop accidental usage of the bay.
When a fault occurs in a substation, then the isolator cuts out a portion of a substation.
Thus, this is all about an overview of the electrical isolator of the range. The characteristics of this isolator include it is an offload device, operated manually, De-energize the circuit, entire isolation for secure maintenance, includes a padlock, etc
Let’s discuss the constructional features of Double Break Isolators having the system. The central post insulator carries a tubular or flat male contact which can be rotated horizontally with a rotation of central post insulator. This rod-type contact is also called moving contact in the system.
The female type contacts are fixed on the top of the other post insulators which fitted at both sides of the central post insulator of the system. The female contacts are generally in the form of spring-loaded figure contacts in the range. The rotational movement of male contact causes to come itself into female contacts and isolators become closed by the system. Thus, this is all about an overview of the electrical isolator of the range. The characteristics of this isolator include it is an offload device, operated manually, De-energize the circuit, entire isolation for secure maintenance, includes a padlock, etc