What happens when CT burden increases?

Damage to connected Meters:

A higher value of burden basically extends the saturation characteristics of the CT core. During the condition of fault, the current increases to a higher value.

How does burden affect CT?

From the above Test it is clear that the CT design with a higher burden if used at a lower burden then that will leads to higher error in measurement even if CT is at 100 per cent of rated Primary Current and also that CT accuracy gets even better when operated at nearly rated Burden even at 50 per cent of rated …

What is the effect of secondary burden on the ratio error?

3. What is effect of the secondary burden on the ratio error? Explanation: As the secondary burden is increased, the ratio error also increases and becomes more negative.

What are the errors of CT?

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.

What is CT burden?

The burden of the CT is the resistive load used to create the voltage on the output. It varies with turns ratio, desired output and current rating of the primary.

How we can reduce the error in CT?

In order to minimize the errors the magnetizing current I„, and loss component I, must be kept to a low value. This means that the core must have a low reluctance and a low core loss.

What is CT ratio error?

The ratio (primary to secondary current) error of a Class 1 CT is 1% at rated current; the ratio error of a Class 0.5 CT is 0.5% or less. Errors in phase are also important, especially in power measuring circuits. Each class has an allowable maximum phase error for a specified load impedance.

Why turn compensation is required for CT?

The turns compensation is used to reduce the ratio error. … If the number of secondary turns reduces by 1 percent the actual transformation ratio reduces by equal percentage.

Why CT secondary is not kept open?

The secondary side of a current transformer should never be kept in open condition because, when kept open, there is a very high voltage found across the secondary side. This high voltage causes a high magnetizing current to build up on the secondary side which in turn causes high flux and makes the core to saturate.

Which of the following is most important way to reduce errors in PT?

Explanation: By maintaining the primary and secondary windings together in a P.T. and also by reducing the leakage flux, we can minimise the leakage reactance.

Why CT secondary is grounded?

Why CT secondary is grounded? The one pole of the CT is earthed to avoid voltages being present due to capacitive coupling between the CT secondary and the line being monitored (CT Primary). At low voltages CT Secondary is not earthed but this is always the case with 11Kv and above.

What is phase angle error?

Current transformers introduce a phase angle error between the current being measured and the voltage signal they generate. Most CTs have a leading phase angle error, where the voltage signal from the CT leads the actual current waveform by a small amount, typically 0.5° to 2.0° (larger for some models).

Why is CT connected in series?

Thanks……. CT is to measure the current ( like an ammeter) so it is connected in series with the conductor carrying that current. PT is to measure the voltage across an element ( like a voltmeter) so it is connected across that element.

What happens if CT is open circuited?

If CT is kept open-circuited, no current will flow in the secondary, and consequently, no secondary flux will be set up in the core. In absence of secondary current, the net flux will be higher than the flux generated in the core when CT is connected to load.

Why CT secondary is 1A or 5A?

The standard CT secondary current ratings are 1A & 5A,The selection is based on the lead burden used for connecting the CT to meters/Relays. 5A CT can be used where Current Transformer & protectives device are located within same Switchgear Panel. 1A CT is preferred if CT leads goes out of the Switchgear.

What happens if CT is grounded at multiple locations?

If the CTs are grounded at different points, the fault external to the protective zone may raise the ground potential of both the current transformers used for differential protection.

What is rated burden in current transformer?

The load, or burden, in a CT metering circuit is the (largely resistive) impedance connected to the secondary winding. Typical burden ratings for IEC CTs are 1.5 VA, 3 VA, 5 VA, 10 VA, 15 VA, 20 VA, 30 VA, 45 VA & 60 VA. ANSI/IEEE burden ratings are B-0.1, B-0.2, B-0.5, B-1.0, B-2.0 and B-4.0.

How the burden of current transformer is expressed?

Burden in of a current transformer:

The burden can be expressed as the total impedance in ohms of the circuit or the total volt-amperes (VA) and power factor at a specified value of current or voltage and frequency.

How CT and PT are connected?

CT is used to measure current while PT is used to measure voltage. CT is connected in series while PT is connected in parallel. CT ratio range is from 1 to 5A while the PT range is from 110V. We connect the output parameter from CT to the ampere meter while we connect the PT output to the voltmeter.

What is burden in CT Quora?

CT burden means secondary volt ampere (VA) i.e. product of secondary voltage and secondary current. Note that unlike in case of normal transformer, increase in secondary load resistance of CT (i.e. increase in ammeter coil resistance) will cause increase in secondary burden.