Match the following sources of error in a CT with their corresponding causes

Error Type		Cause
1.	Ratio Error	A.	Leakage flux in windings
2.	Phase Angle Error	B.	Magnetising current requirement
3.	Hysteresis Error	C.	Non-ideal core material properties
4.	Leakage Reactance Error	D.	Residual magnetism in the core

Matching the Error Types and Causes in Current Transformers (CTs):

In a Current Transformer (CT), various sources of errors arise due to the physical and electrical characteristics of the transformer. These errors are classified into different types, and each error type has specific causes associated with it. Understanding the relationship between these errors and their causes is crucial for ensuring the accurate performance of CTs in electrical systems.

The correct matching of error types with their causes is:

Option 3: 1 → B, 2 → C, 3 → D, 4 → A

Let us analyze each error type and its corresponding cause:

1. Ratio Error (1 → B):

Explanation: Ratio error occurs when there is a discrepancy between the actual transformation ratio of the CT and its nominal or designed transformation ratio. This discrepancy primarily arises due to the magnetizing current requirement of the core. Magnetizing current is the current needed to establish the magnetic flux in the CT core, and it does not contribute to the secondary current. As a result, it causes a deviation in the actual ratio of primary to secondary currents, leading to ratio error.

Key Cause: Magnetizing current requirement (B).

2. Phase Angle Error (2 → C):

Explanation: Phase angle error is the angular displacement between the primary current and the secondary current of a CT. Ideally, the primary and secondary currents should be in phase (for a purely resistive burden). However, due to non-ideal properties of the core material (such as hysteresis and eddy current losses), there is a phase shift between the two currents. These non-ideal core properties affect the accuracy of the CT and result in phase angle error.

Key Cause: Non-ideal core material properties (C).

3. Hysteresis Error (3 → D):

Explanation: Hysteresis error is caused by the residual magnetism or remanence in the CT core. When the core is magnetized by the primary current, some residual magnetism remains in the core even after the current is removed. This residual flux affects the accuracy of the CT and leads to hysteresis error. It is particularly significant in applications where the CT is subjected to varying primary currents.

Key Cause: Residual magnetism in the core (D).

4. Leakage Reactance Error (4 → A):

Explanation: Leakage reactance error arises due to the leakage flux in the CT windings. Leakage flux is the portion of the magnetic flux that does not link both the primary and secondary windings. This flux creates reactance in the windings, which impacts the accuracy of the CT. The leakage reactance causes a voltage drop in the windings, thereby introducing errors in the secondary current.

Key Cause: Leakage flux in windings (A).

Important Information

To further understand the analysis, let’s evaluate the other options:

Option 1: 1 → A, 2 → B, 3 → D, 4 → C

This option incorrectly associates the causes with the error types. For example, it matches ratio error with "leakage flux in windings" (A), which is incorrect because ratio error is primarily caused by the magnetizing current requirement (B). Similarly, other mismatches make this option incorrect.

Option 2: 1 → B, 2 → A, 3 → D, 4 → C

This option also contains incorrect associations. For instance, it matches phase angle error with "leakage flux in windings" (A), which is incorrect because phase angle error is caused by non-ideal core material properties (C). The other pairings are also mismatched.

Option 4: 1 → B, 2 → A, 3 → C, 4 → D

In this option, hysteresis error is incorrectly matched with "non-ideal core material properties" (C) instead of "residual magnetism in the core" (D). Leakage reactance error is also mismatched with "residual magnetism in the core" (D) instead of "leakage flux in windings" (A).

Conclusion:

Understanding the sources of errors in CTs and their respective causes is essential for ensuring the accuracy and reliability of these devices. The correct matching of error types with their causes is as follows:

• Ratio Error: Magnetizing current requirement (B).
• Phase Angle Error: Non-ideal core material properties (C).
• Hysteresis Error: Residual magnetism in the core (D).
• Leakage Reactance Error: Leakage flux in windings (A).

Option 3 correctly identifies these relationships, making it the correct choice.