Is specialized in designing, manufacturing for power transformers ,furnace transformers and reactor.

Influence of Current Transformer Overload on Metering

Influence of current transformer overload on metering

A 35KV wholesale user of our bureau has a metering current transformer model of lcz-35-100 / 5 and an energy meter model of dss331 and 3 100V3 1.5(6)A Due to continuous drought, the user's own hydropower output decreased. The current reached 162a at peak load in December 2001, which seriously exceeded the rated current of current transformer, resulting in the loss rate of 100m line as high as 19.6%. Therefore, we test and analyze the measurement error of current transformer when it is overloaded.

1. Influence of serious overload of current transformer on current transformer body

(1) Test object: current transformer, model: lcz-35-100 / 5; Secondary rated load: 50VA, accuracy level: 0.2; Manufacturer: Chongqing high voltage electrical appliance factory, No. 069.

Power factor during test: 0.8.

(2) When the load current is 5% to 165% of the rated current of the current transformer (current transformer regulation stipulates that 5%, 20%, 100% and 120% of the rated current are selected for the verification load point), the error (ratio difference and angle difference) is shown in Table 1.

Table 1

(3) It can be seen from the test data that when the load current is within 120% of the rated current, the greater the load, the smaller the error of current transformer; When the load current is between 120% 165% of the rated current, the error of current transformer increases with the increase of load current, but gradually tends to balance within the allowable range. This is because in the design of current transformer, the minimum saturation multiple determining the overload capacity of current transformer is generally 2 3 times of rated current; With the increasingly mature and advanced manufacturing technology of current transformers, some current transformers can withstand dozens of times of rated current in a short time.

2 Influence of current transformer overload on electric energy meter

When the current transformer is overloaded, it will not be saturated in a certain range, the secondary current will increase proportionally, and the supporting electric energy meter will also be overloaded.

Power factor during test: 1.0.

(2) In order to match the current transformer test, the load current is selected to be 10% 533% of the calibration current IB of the electric energy meter (jjg596-1999 regulation stipulates that when the power factor is 1.0, the verification points are 10%, 50%, 100% and 400% of the calibration current), and the error is shown in Table 2.

Table 2

The error r% curve when the above test error exceeds the rated maximum current Imax (400% IB) of the electric energy meter is shown in Figure 1.

Fig. 1 error curve of electric energy meter under overload

It can be seen that when the actual current is greater than the maximum rated current Imax of the electric energy meter, the electric energy meter will not burn due to certain overload capacity, but the negative error of the electric energy meter is large, and with the increase of overload current, the negative error becomes larger and larger, that is, the electric energy meter becomes slower and slower.

3 conclusion

When the current transformer is overloaded for a short time, the current transformer can operate normally, and the secondary current exceeds the maximum rated current of the electric energy meter, resulting in large negative error of the electric energy meter and slow measurement.

Because the overload of current transformer has certain concealment, it is impossible to verify a correction coefficient when making up the power. Therefore, it is necessary to reasonably configure current transformer, strengthen the supervision and inspection of power load and reduce power loss.

Influence of Current Transformer Overload on Metering 1

recommended articles
Case News
1 What are the advantages and disadvantages of machine winding and manual winding in the manufacture of transformer?The advantages of machine wound transformer are h...
Several common detection wiring modes of transformer:The transformer winding deformation tester is mainly composed of main measuring unit and notebook computer, para...
The working principle of current transformer is similar to that of transformer. Its basic working principle is to work according to the electric magnetic electric co...
Voltage transformer and current transformer have the same point. They all use the working principle of electricity magnetism electricity. As shown in Figure 1 belo...
Transformer winding machine is a special equipment used to wind transformer coils. In the process of transformer coil production, winding equipment is divided accord...
Comparison of power transformers:1 What are the advantages and disadvantages of machine winding and manual winding in the manufacture of transformer?The advantages o...
Shunt capacitor, formerly known as phase-shifting capacitor. It is mainly used to compensate the reactive power of inductive load in power system, so as to improve p...
Working principle of power transformerAs for the power transformer, it is a special transformer whose output and input share a set of coils. The step-up and step-dow...
Introduction to working principle of power transformerThe high-voltage winding used in domestic transformers is generally connected into Y connection method, and the...
The secondary parameters of current transformer include transformation ratio and accuracy level.For the current transformer for protection, the accuracy level shall ...
no data
Copyright © 2024 NINGBO VILLE ENTERPRISE CO.,LTD. - https://www.villeelectric.com/ | Sitemap
Customer service