## Can Protection CT be used as Metering CT & Vice Versa?

Protection Current Transformer (CT) and Metering CT are two different types of CT as per their requirement and hence design. Therefore, Protection class CT should not be used as Metering CT. Similarly, a Metering Current Transformer should not be used for protection purpose. Let the discuss the reason behind this. Why can’t we use Protection … Read more

## Accuracy Class of Current Transformer

Accuracy Class of Current Transformer (CT) is defined in Indian Standard IS 2705 Part-2 and Part-3. This accuracy class of CT is defined so as to provide the permissible error in the current measurement of CT. As we know that, there are three types of errors defined for a CT: Current Error (or Ratio Error), … Read more

## Composite Error of CT – Definition, Calculation & Formula

Definition: Composite Error of a Current Transformer (CT) is defined as the rms value of difference between the ideal secondary current and the actual secondary current. It includes ratio error, phase error and the effect of harmonics present in the exciting current. Composite error is used to express the accuracy of protection class CT. You … Read more

## What is 3.5 or 4.5 Digit Meter Display?

If you go through the catalog of any instrument having digital display, you may notice that its display is given like three and half (3½) or four and half (4½) LCD display. So what does this mean or what information does this provide? Basically, there are two types of digits in digital display: Full digit … Read more

## Phase Sequence Indicator – Working and Importance

Phase Sequence Indicator is an instrument which identifies the phase sequence of three phase supply system. Phase sequence or often called phase rotation of 3 phase supply system is defined as the sequence or order in which voltage in R, Y and B phase is attains their maximum value. Normally the phase sequence is RYB. … Read more

The main advantage of Moving Iron Instrument is that it can measure AC as well as DC quantities. Though this instrument is responsive to DC, it suffers from hysteresis error which causes an appreciable error in the measurement of DC. Therefore, it is rarely used for DC applications. This is one of the main disadvantages … Read more

## Concept of Rogowski Coil and its Working

What is Rogowski Coil? Rogowski Coil is an electrical device used for the measurement of alternating (AC) current. It can measure high speed transient current, pulsed current as well as power frequency AC current. It is simply a toroidal coil named after German physicist Walter Rogowski. A Rogowski coil is evenly wound coil on a … Read more

## Need of Motor and Phase Rotation Indicator?

What is Motor and Phase Rotation Indicator? Motor and Phase Rotation Indicator is an instrument capable of indicating the correct rotation of motor corresponding to the marked phase connection on motor terminal box. It can also indicates the correct phase sequence of three phase system. Motor terminal box have terminals marked as R, Y and … Read more

## Maxwell Bridge-Measurement of Inductance

Maxwell Bridge is used for the measurement of Self-Inductance. Like other bridge, this method also works on balancing of bridge. Balancing of bridge is achieved when there is no current through the detector. Don’t worry we will be discussing everything in detail in this post. Maxwell’s Bridge employs the comparison of test specimen variable standard … Read more

## RVDT – Construction and Working Principle

What is RVDT? Definition: Rotary Variable Differential Transformer or RVDT is an inductive transducer which converts angular displace to an electrical signal. Unlike LVDT, the input of this transducer is differential value of rotary variable i.e. angular rotation (dƟ) to generate voltage output. Construction: Like every transformer, RVDT has two types of winding i.e. Primary … Read more