BURDEN ON THE TRANSFORMER AND PROTECTION SYSTEM

Burden on the transformer and protection system - The impedance of the secondary circuit in ohms and power-factor. The burden is usually Expressed as the apparent power in voltamperes absorbed at a specified power-factor and at the rated secondary current.

specification grade accuracy and burden based on ANSI / IEEE for transformer measurements.

Thus, a burden can be expressed in two ways, namely: 

1. A burden expressed as the total impedance of the secondary circuit in units of Ohms. This definition is used in standard ANSI / IEEE. Table 1 shows the burden by ANSI.
2. A burden is expressed in the form of real power voltamperes (Apparent power, VA) at a specified power factor at the secondary flow identifier (Rated Secondary Current). This definition is used in the standard IEC60044-1. Standard IEC 60044-1 requires manufacturers to perform testing using the burden on certain values ​​and 0.8 lagging power factor as the quote below are based on the IEC60044-1 standard.

keep in mind! that class accuracy and Burden are 2 things are interrelated, so it is always defined simultaneously. Accuracy value will shift from a predetermined value when the burden that used larger or smaller than a predetermined limit burden. 

While we know, the definition of the secondary circuit is a circuit which is connected to the secondary coil of the transformer currents. Secondary circuit can include cable, or measuring equipment and protection. 

Thus, the notion of burden on current transformer covers all components connected to the secondary coil of the transformer flow meters such as equipment or protection, connectors, cables, lights and other indicators. In the example above, the burden includes connecting cable impedance and measuring equipment or protective 

Since the resistance of the connecting cable between the current transformer secondary terminal equipment or protective measure greatly affect the performance of a current transformer, then some of the following should be noted. 

• If the measuring equipment or protective located away from the secondary terminal, it should be used with output current transformer secondary current is small, for example 1 ampere. Using a current transformer with output 5 amperes for measuring devices located away from the secondary terminals, will lead VA absorbed by the much larger cable.
• To ensure accuracy in the range of values ​​corresponding to the results of the manufacturer, then the value of the burden should be in the range of 25% to 100% of rated burdennya (for CT with IEC60044-1 standard) or in the range of rated burdennya to ANSI / IEEE C57.13
• The use of a much larger burden or smaller than the burden identifier (rated burden), will cause an error ratio (ratio error and phase shift) becomes larger.
• Use of burden that is not appropriate, will also result in a shift in the value of FS or ALF, which can cause damage to the measuring equipment or faster CT saturation.

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