Difference between current and voltage transformer pdf

Posted on Saturday, June 12, 2021 9:43:36 PM Posted by Cuasimodo R. - 13.06.2021 and pdf, pdf free download 2 Comments

difference between current and voltage transformer pdf

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Electrical Academia.

Difference between Current Transformer and Potential Transformer

Category: Electricity Specification: S-E rev. These specifications apply to instrument transformers which are intended to be used in revenue metering. Specifications for current transformers are applicable only for solid core devices. These specifications are issued pursuant to subsection 12 1 of the Electricity and Gas Inspection Regulations. A designation assigned to a measuring instrument transformer the errors of which remain within specified limits under prescribed conditions of use.

The normal operating voltage of a voltage transformer upon which the accuracy performance is based. The property of the circuit connected to the secondary winding that determines the active and reactive power at the secondary terminals. The burden is expressed either as total ohms impedance with the effective resistance and reactance components, or as the total volt-amperes and power factor at the specified value of current or voltage, and frequency.

A voltage transformer comprising a capacitor divider unit and an electromagnetic unit so designed and connected that the secondary voltage of the electromagnetic unit is substantially proportional to the primary voltage, and differs in phase from it by an angle which is approximately zero for an appropriate direction of connections and rated frequency.

A combination of voltage and current measuring transformers in a single tank or assembly. Also known as a "metering outfit". The rating factor may be 1. The rating factor of tapped-secondary or multi-ratio transformers applies to the highest ratio, unless otherwise stated. A measuring instrument transformer in which the secondary current, in normal conditions of use, is substantially proportional to the primary current and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections.

A current transformer equipped with two primary windings suitable for series or parallel connection and common to all secondary coils and magnetic circuits. One current transformer which has two secondary coils each on a separate magnetic circuit with both magnetic circuits excited by the same primary winding or windings.

The secondary coils may be tapped or untapped. One voltage transformer which has two secondary windings on the same magnetic circuit insulated from each other and the primary. Either or both of the secondary windings may be used for measurement or control. A multi-ratio current transformer having two ratios which are not necessarily in the relation of two to one.

The highest continuous root-mean-square steady-state voltage for which the equipment insulation is designed. A measuring transformer which is intended to reproduce in its secondary circuit, in a definite and known proportion, the current or voltage of its primary circuit with the phase relations substantially preserved. One current transformer from which more than one ratio can be obtained by the use of taps or series-multiple connection.

One current transformer which has three or more secondary coils each on a separate magnetic circuit with all magnetic circuits excited by the same primary winding. The ratio of the true power factor to the measured power factor. It is a function of both the phase angle of the instrument transformer and the power factor of the primary circuit being measured. Note: The phase angle correction factor is the factor which corrects for the phase displacement of the current or voltage or both, due to the instrument transformer phase angle.

The measured watts or watt hours in the secondary circuits of instrument transformers must be multiplied by the phase angle correction factor and the true ratio to obtain the true primary watts or watt hours. The combination of voltage values which characterize the insulation of an instrument transformer to withstand dielectric stresses.

The value of the apparent power in volt-amperes at a specific power factor which the transformer is intended to supply to the secondary circuit at the rated secondary current or voltage and with rated burden connected to it.

The ratio of the true ratio to the marked ratio. The primary current or voltage is equal to the secondary current or voltage multiplied by the marked ratio times the ratio correction factor. Accuracy designation for current transformers shall be such that the accuracy class is identified, followed by the letter B, followed by the maximum standard burden applicable for the accuracy rating. Accuracy designation for voltage transformers shall be such that the accuracy class is identified, followed by all the standard burdens applicable for the accuracy rating.

A current transformer which has two separate primary windings each completely insulated for the rated insulation level of the transformer. This type of current transformer is for use on a three-wire, single-phase service. Note: These transformers may have two primary windings, one secondary winding and one core assembled as a single unit; or have two primary windings, two secondary windings and two cores assembled as separate units and mounted on one base with the secondaries connected permanently in parallel to a single terminal block.

The secondary current in both cases is proportional to the phasor sum of the primary currents. The ratio correction factor multiplied by the phase angle correction factor for a specified primary circuit power factor.

The ratio of the root-mean-square primary value to the root-mean-square secondary value under specified conditions, with sinusoidal current or voltage in the primary winding. The manufacturer's designation for transformers having different nominal currents or voltages, but which are similar in:.

The level of power frequency voltage which identifies the system of insulation levels and associated tests applicable to the transformer. A measuring instrument transformer in which the secondary voltage, in normal conditions of use, is substantially proportional to the primary voltage and differs from it by an angle which is approximately zero for an appropriate direction of the connections. In general, terminal markings shall identify the primary and secondary windings, the winding sections if any , the relative polarities of windings and winding sections, and the intermediate tappings if any.

Terminal markings of capacitor voltage transformers shall meet Canadian marking requirements of section 6. If the transformer is contained within another device such as a power transformer or a metering outfit, the nameplate shall be mounted on the exterior of the device in such a manner as to be readily visible i. The nameplate shall not be mounted on the terminal cover unless the cover remains permanently attached to the exterior of the transformer by a physical means such as a non-removable hinge or similar arrangement.

For multi ratio current transformers, if only one accuracy rating is assigned, it shall apply to all ratios. The relationships between the limits of the ratio correction factors RCFs and the phase angle for the limiting values of the TCFs specified in Table 4 are shown in the parallelograms in Figure 1.

These limits also apply at the maximum continuous current rating factor RF. The RF can be 1. The relationships between the limits of the ratio correction factors and the phase angle for the limiting values of the transformer correction factors TCFs specified in Table 4 are provided by parallelograms that are plotted on graphs in which a phase angle correction factor in minutes appears on the x-axis and a ratio correction factor appears on the y-axis.

The parallelograms defining the limiting values of the TCFs for current transformers are bound by vertices. For a 0. Where a double accuracy designation is specified e. The relationships between the limits of the ratio correction factors and the phase angle for the limiting values of the TCFs specified in Table 5 are shown in the parallelogram in Figure 2.

The relationships between the limits of the ratio correction factors and the phase angle for the limiting values of the transformer correction factors TCFs specified in Table 5 are provided by parallelograms that are plotted on graphs in which a phase angle correction factor in minutes appears on the x-axis and a ratio correction factor appears on the y-axis.

The parallelograms defining the limiting values of the TCFs for voltage transformers are bound by vertices. The purpose of revision 1 is to make clarifications to the parallelogram of Figure 1: Limits of 0. E-4 , subsection 9 4 3. Accuracy-rating voltage The normal operating voltage of a voltage transformer upon which the accuracy performance is based. Burden The property of the circuit connected to the secondary winding that determines the active and reactive power at the secondary terminals.

Capacitor voltage transformer A voltage transformer comprising a capacitor divider unit and an electromagnetic unit so designed and connected that the secondary voltage of the electromagnetic unit is substantially proportional to the primary voltage, and differs in phase from it by an angle which is approximately zero for an appropriate direction of connections and rated frequency.

Combined instrument transformer A combination of voltage and current measuring transformers in a single tank or assembly. Current transformer A measuring instrument transformer in which the secondary current, in normal conditions of use, is substantially proportional to the primary current and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections.

Double-primary current transformer A current transformer equipped with two primary windings suitable for series or parallel connection and common to all secondary coils and magnetic circuits. Double-ratio current transformer A multi-ratio current transformer which has two ratios which are in the ratio of two to one.

Double-secondary current transformer One current transformer which has two secondary coils each on a separate magnetic circuit with both magnetic circuits excited by the same primary winding or windings. Double-secondary voltage transformer One voltage transformer which has two secondary windings on the same magnetic circuit insulated from each other and the primary.

Dual-ratio current transformer A multi-ratio current transformer having two ratios which are not necessarily in the relation of two to one. Highest voltage for equipment The highest continuous root-mean-square steady-state voltage for which the equipment insulation is designed. Instrument transformer A measuring transformer which is intended to reproduce in its secondary circuit, in a definite and known proportion, the current or voltage of its primary circuit with the phase relations substantially preserved.

Marked ratio The ratio of the rated primary value to the rated secondary value as stated on the nameplate. Multi-ratio current transformer One current transformer from which more than one ratio can be obtained by the use of taps or series-multiple connection. Multiple secondary current transformer One current transformer which has three or more secondary coils each on a separate magnetic circuit with all magnetic circuits excited by the same primary winding.

Percent ratio error of an instrument transformer The difference between the ratio correction factor and unity expressed in per cent. Phase angle correction factor The ratio of the true power factor to the measured power factor. Note Example: 0. Note These limits also apply at the maximum continuous current rating factor RF. Limits of 0. Phase angle of an instrument transformer The phase displacement between the primary and secondary values.

Where: RCF is the ratio correction factor and TCF is the transformer correction factor Rated insulation level The combination of voltage values which characterize the insulation of an instrument transformer to withstand dielectric stresses.

Rated output The value of the apparent power in volt-amperes at a specific power factor which the transformer is intended to supply to the secondary circuit at the rated secondary current or voltage and with rated burden connected to it. Rated primary current of a current transformer The current selected for the basis of performance specifications. Rated primary voltage of a voltage transformer The voltage selected for the basis of performance specifications.

Rated secondary current The rated primary current divided by the marked ratio. Rated secondary voltage The rated primary voltage divided by the marked ratio.

Ratio correction factor The ratio of the true ratio to the marked ratio. Accuracy designation for current transformer Accuracy designation for current transformers shall be such that the accuracy class is identified, followed by the letter B, followed by the maximum standard burden applicable for the accuracy rating.

Accuracy designation for voltage transformer Accuracy designation for voltage transformers shall be such that the accuracy class is identified, followed by all the standard burdens applicable for the accuracy rating. Three-wire current transformer A current transformer which has two separate primary windings each completely insulated for the rated insulation level of the transformer.

Transformer correction factor The ratio correction factor multiplied by the phase angle correction factor for a specified primary circuit power factor. True ratio The ratio of the root-mean-square primary value to the root-mean-square secondary value under specified conditions, with sinusoidal current or voltage in the primary winding.

Type The manufacturer's designation for transformers having different nominal currents or voltages, but which are similar in: measurement characteristics model and construction Voltage classification The level of power frequency voltage which identifies the system of insulation levels and associated tests applicable to the transformer.

Voltage transformer A measuring instrument transformer in which the secondary voltage, in normal conditions of use, is substantially proportional to the primary voltage and differs from it by an angle which is approximately zero for an appropriate direction of the connections.

Step-up and Step-down Transformers

Both current transformers and potential transformers are considered to be instrument transformers. These transformers are responsible for measuring whether power systems are both precise and safe. Both also use magnetic circuitry in their primary and secondary winding to operate. But there are distinct differences between these two instrument transformers. Current transformers, also known as CTs, are used to measure alternating current.

Current Transformers CT and Potential Transformers PT are used to measure the current and voltage in a circuit of the order of hundreds of amperes and volts respectively. A CT has large number of turns on its secondary winding, but very few turns on its primary winding. The primary winding is connected in series with the load so that it carries full load current. A low voltage range ammeter A is connected across the secondary winding terminals. Secondary of the CT is practically short circuited since the ammeter resistance is very low. It should be remembered that secondary of the CT should not be made open as it draws heavy current and damages the primary winding of the CT. A PT has large number of turns in the primary and fewer turns in the secondary and hence it steps down the voltage.


There are several types of.


Current transformer

A current transformer CT is a type of transformer that is used to reduce or multiply an alternating current AC. It produces a current in its secondary which is proportional to the current in its primary. Current transformers, along with voltage or potential transformers, are instrument transformers.

Technical information on Kappa products Instrument transformers are used for measurement and protective application, together with equipment such as meters and relays. Their role in electrical systems is of primary importance as they are a means of "stepping down" the current or voltage of a system to measurable values, such as 5A or 1A in the case of a current transformers or V or V in the case of a voltage transformer. This offers the advantage that measurement and protective equipment can be standardized on a few values of current and voltage.

The electrical instruments are not directly connected to the meters or control apparatus of high voltage for safety purpose. The instrument transformers like voltage transformer and current transformer are used for connecting the electrical instruments to the measuring instruments. These transformers reduce the voltage and current from high value to the low value which can be measured by conventional instruments. The construction of the current and potential transformer is similar as both have the magnetic circuit in their primary and secondary winding.

Instrument Transformers - CT and PT

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Difference Between Current Transformer (CT) & Potential Transformer (PT)

The load consists Technical notes Technical notes Primary voltage Primary voltage. Accessories Description Accessory sealable terminal cover. Accessories Description Accessory sealable terminal cover Screw type for wall mounting. BSA02 2 single-phase input current summation transformer It effects the vectorial sum of the currents of many lines in just one voltage system. It is essential when the main C. Catalog excerpts.

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Equality of voltage and current between the primary and secondary sides of a transformer, however, is not the norm for all transformers. Notice how the secondary voltage is approximately ten times less than the primary voltage 0. What we have here is a device that steps the voltage down by a factor of ten and current up by a factor of ten:. Turns ratio of yields primary: secondary voltage ratio and primary: secondary current ratio. This is a very useful device, indeed.

Combined current/voltage transformer PVA

COMMENT 2

  • Current Transformers CT and Potential Transformers PT are used to measure the current and voltage in a circuit of the order of hundreds of amperes and volts respectively. Leo C. - 17.06.2021 at 07:25
  • Category: Electricity Specification: S-E rev. Agripina P. - 19.06.2021 at 07:27

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