Why current transformers are required in protective relaying scheme?
Current transformers (CTs) are used to monitor the current (or lack of) in high-voltage systems, and their secondary outputs controls the behaviour of protection-system relays. The CTs (1) reduce the current to values that match the current ratings of the protective relays, and (2) electrically-isolate the relays from the high-voltage system.
CTs, as well as potential transformers, are called instrument transformers. If the current in the circuit is high then CT will reduce the current and produce a accurately proportional current required in the circuit.It is commonly used in metering systems,protective relays. Answer A CT also has the important function of electrically-isolating the secondary circuit from the primary circuit -very important in high-voltage applications.
Current transformers are used to supply a ratio of the current flowing through the breaker to equipment such as protective relays and meters. If the CTs are used for protection, they are placed around a breaker to provide different, ideally overlapping, zones of protection.
A current transformer (CT) is used for measurement of alternating electric currents. Current transformers, together with voltage (or potential) transformers (VT or PT), are known as instrument transformers. When current in a circuit is too high to apply directly to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments. A current transformer isolates the measuring instruments from… Read More
What are the functions of current transformers and the difference between current transformers and voltage transformers?
To sense the current flow across the current transformers and to monitor the current ratings. In current transformers no voltage variations occurs. but in voltage transformers it is mainly used to increase or decrease the voltage value.
Yes up to a certain amperage. In my area you can go 3 phase up to 200 amps. Any services larger that that, the power authority requires current transformers. For higher voltages and current, current transformers and potential transformers are required. These are installed in what is called a metering cabinet.
The term, 'instrument transformer', is applied to current transformers and voltage transformers (known, in North America, as 'potential transformers'). The primary windings of instrument transformers are connected to high-voltage systems, and their secondary windings provide outputs to measuring instruments or protective relays. They also provide isolation from the high-voltage system for the purpose of safety.
'Potential transformers' (US terminology) or 'voltage transformers' (UK terminology) are, together with 'current transformers', collectively called 'instrument transformers', and are used to safely measure/monitor voltages and currents in high-voltage systems. Potential transformers are used to reduce the voltage-level of a high-voltage circuit to a lower voltage which can then be read using an ordinary voltmeter; at the same time, it electrically-isolates the high-voltage system for the purpose of safety. Potential transformers, together with current transformers… Read More
A current transformer is used for measurement of alternating electric currents. Current transformers, together with voltage transformers are known as instrument transformers.
current transformers are used for metering and for protection purpose
current transformers used for relaying and metering purposes should ideally be installed on all three phases. For specific purposes, you may only use CT's on two phases, such as when implementing certain types of ground relaying, but even in this instance three phase CT's are necessary for phase to phase fault protection. I know it is sometimes a utility practice to only meter off of two phases, as long as system voltages and currents are… Read More
No. Transformers are used in circuits with Alternating Current. Transformers work on the principle of a "changing" magnetic field inducing a current in a conductor, and you don't get that "changing" field with Direct Current.
Yes, we can connect transformers in parallel. For this operation we should know the polarity of the transformers. If we connect transformers in parallel the total output current is equal to the sum of the 2 transformers secondary current.
Yes, certain types of relays can be activated by current transformers.
Almost all of the equipment inside of a substation is used for the purpose of protection. The circuit breakers and power transformers in the substation are equipped with current transformers (CTs) that step down the current passing through the equipment to a level that can be read by protective relays. These protective relays can cause the breakers to trip upon many different events including under/overvoltage, current spikes, frequency issues, transformer/bus differential, etc. The breakers in… Read More
Current and voltage transformers are not 'connected in' switch gear. These instrument transformers are used to monitor the currents and voltages in a high-voltage system, in order to operate protective relays. In the event of electrical faults, it is these protective relays that act to trip the appropriate switchgear to disconnect the fault. This is done by applying a d.c. voltage to switchgear's trip coil, which disengages the trip mechanism. Having said that, CTs are… Read More
Not unless you want to see some cool pyrotechnics! Circulating current will be induced between the two transformers if this is done. This current magnitude will be limited by the phase angle difference and the impedance of the two transformers. It is likely this current will be high enough to cause protective devices to operate regardless of loading on the secondary - fusing, overcurrent relays, sudden pressure relays, etc. If the impedance of the transformers… Read More
An inverter is an electrical device that converts direct current (DC) to alternating current (AC); the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits.
Certain electric devices such as cordless telephones have small transformers that plug into walls.what do the transformers do?
Transformers are relatively simple devices which change both the current and the voltage of an electric source without affecting the total amount of power being given. Power, as the product of current and voltage, is mostly conserved as transformers are used, but the current and voltage changes. If the device needs just half the voltage of what is coming out of your wall (240v in Australia), then it will 'step down' this voltage by half… Read More
A fuse is the simplest protective device for over current in an electric circuit.
The current is automatically stepped up or down when the voltge is stepped down or up by a transformer. Most transformers are designed for a constant voltage, and the current varies depending on the load. Current transformers are also made to detect the current in a power cable so that it can be measured. Another Answer It's a misconception that transformers step current up or down (with the exception of current transformers, that is!). Transformers… Read More
I am aware that Class TPS current transformers have a Low Leakage Flux design
transformers cannot amplify!
Current transformers are used to measure electric currents. When current in a circuit is too high to directly apply to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments.
Current transformers are not voltage transformers. Current transformer are used for metering or protection purposes, with single turn primary. Generally the secondary current is either 1Amps or 5Amps.
Instrumental transformers are potential transformers and current transformers,they are used to measuring and protecting purposes at power systems
yes its does the higher the current will blow out the transformers
Current transformers are used to transform high currents to standardized values for control equipment as relays and meters. The primary winding in a current transformer is incorporated in the line and carries the current flowing in the network. The magnitude of the secondary current is dependent of the ratio of the transformer. A current transformer (CT) is a type of instrument transformer designed to provide a current in its secondary winding proportional to the alternating… Read More
Current transformer and voltage transformer . This transformers are actually measuring instruments which measures the quantity of current and voltage coming out of the substation.
AC current or DC current can be used in transformers. A transformer is made of two coils of wire, the input coil induces a current into the output coil. Transformers change the voltage either up (step up transformer) or down (step down transformer). The amount of change in voltage is dependent solely on the number of windings in both coils in the transformer. DC transformers work exactly the same way AC transformers do.
By direct from the manufacturer! Current & Potential Transformers
A transformer is a device that changes an electrical voltage or current from one level to another. (In radio frequency applications, it is used to couple the RF electronic circuits.) Transformers are used to: Convert high voltage alternating current (AC) to desired low voltage alternating current (AC). Such transformers are called step down transformers. Convert low voltage alternating current (AC) to desired high voltage alternating current (AC). Such transformers are called step up transformers. Electrically… Read More
Current Transformers are connected in the circuit in series.
In a substation there are many items. Circuit Breakers Disconnectors Earth Switches Current Transformers Voltage Transformers Surge Arrestors Power Transformers Insulators
Instrument transformers proportionally step down or reduce large voltage and current values so that they may be safely used on sensitive instruments and components. These instruments and components include ammeters, voltmeters, and overcurrent protection relays. Instrument transformers fall into two distinct categories: potential and current transformers. A potential transformer (PT) is used to supply a low voltage to voltmeters, and a current transformer (CT) supplies manageable current vales for ammeters and overcurrent relays.
Current transformers ('CTs') are used in high-voltage systems to allow the currents flowing in these systems to be measured or to operate protective systems. A CT's secondary winding is isolated from the high-voltage system, allowing measurements to be made, or protective devices to operate, safely. Actually, a CT is a 'step up' transformer, because the terms 'step up' and 'step down', refer to voltages, not currents. For this reason, a CT should NEVER be allowed… Read More
'Instrument transformer' is the collective name for current transformers (CTs) and voltage (or 'potential') transformers (VTs/PTs). These transformers have two functions: to reduce the current or voltage in a high-voltage primary circuit to values that may be measured using regular ammeters or voltmeters ('burdens'), or to provide the current or voltage inputs to protection relays. to electrically-isolate their secondary burdens from the high-voltage primary circuit for the purpose of safety.
CURRENT TRANSFORMERS ARE BROADLY CLASSIFIED AS RING TYPE CTs : A CT which has an opening in the center to accommodate a primary conductor (busbar or cable) through it. BAR -PRIMARY CTs A CT in which the primary winding consists of bar of suitable size and, material forming an integral part of the CT. WOUND TYPE CTs : A CT having a primary winding of more than ane full turn wound on the core. Ring… Read More
WRIGHT. has written: 'CURRENT TRANSFORMERS'
The current that is transferred through cables over long distances is AC. The main reason for this is because it is easier to handle. For example, it is easy to convert an AC current to a higher or a lower voltage with transformers. Transformers don't work for DC.
Well after michal bay finishes his current movie transformers 3: dark of the moon he is not thinking about another one.
H. W Price has written: 'Papers on current transformers' -- subject(s): Electric transformers
Generators actually generate current and transformers convert between current and voltage.
It is known that the value of transformation ratio (actual ratio) is not equal to the turns ratio in current transformers. Also the value is not constant, but depends upon the magnetizing and loss components of the exciting current, the secondary winding load current and its power factor. This means that the secondary winding current is not a constant fraction of the primary winding current but depends upon the factors listed above.
A 'current transformer' is a type of transformer which, together with a 'voltage transformer' (or 'potential transformer' in N America), is classified as being an 'instrument transformer'. It is used to reduce large currents to smaller currents which can be measured safely, and to isolate the primary circuit from the secondary circuit for the purposes of safety. Current transformers are also used to drive protective relays used in high-voltage protection systems.
Cabinets which house Current Transformers
Disconnect the primary source.