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Compute the primary current for (a) I' = 10 A and ZB = 1 , for (b) I' = 13 A and Z³ = 1.3 №. (c) Plot I' versus I for five values of I' which are displayed in the table. Note that we already calculated the primary currents for I' of 5, 8, and 15-A in Example solved in Session 12 (Oct. 2nd). When plotting I' versus I by connecting different points, do your best to clearly show the saturation region of the curve. (d) For reliable relay operation, the fault-to-pickup current ratio with minimum fault current should be greater than two. Determine the minimum fault current for application of this CT and relay with 5-A tap setting. In other words, calculate the minimum fault current for which the relay will trip reliably.

Compute the primary current for (a) I' = 10 A and ZB = 1 , for (b) I' = 13 A and Z³ = 1.3 №. (c) Plot I' versus I for five values of I' which are displayed in the table. Note that we already calculated the primary currents for I' of 5, 8, and 15-A in Example solved in Session 12 (Oct. 2nd). When plotting I' versus I by connecting different points, do your best to clearly show the saturation region of the curve. (d) For reliable relay operation, the fault-to-pickup current ratio with minimum fault current should be greater than two. Determine the minimum fault current for application of this CT and relay with 5-A tap setting. In other words, calculate the minimum fault current for which the relay will trip reliably.

Introductory Circuit Analysis (13th Edition)
Introductory Circuit Analysis (13th Edition)
13th Edition
ISBN:9780133923605
Author:Robert L. Boylestad
Publisher:Robert L. Boylestad
Chapter1: Introduction
Section: Chapter Questions
Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...
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**CO-8 Relay and CT Analysis** A CO-8 relay with a current tap setting of 5 amperes is used with a 100:5 current transformer (CT). The CT secondary current \( I' \) serves as the input to the relay operating coil. The CO-8 relay burden for various relay input currents is listed in the table below: | **CO-8 relay input current \( I' \), A** | 5 | 8 | 10 | 13 | 15 | |-----------------------------------------|----|----|----|----|----| | **CO-8 relay burden \( Z_B, \, \Omega \)** | 0.5| 0.8| 1.0| 1.3| 1.5| The graph represents the relationship between the secondary exciting voltage \( E' \) and the exciting current \( I_e \) for the CT. **Graph Explanation:** - **X-axis:** Represents the exciting current, \( I_e \). - **Y-axis:** Represents the secondary exciting voltage, \( E' \). - Multiple curves depict different CT ratios ranging from 50:5 to 600:5. The table next to the graph provides the secondary resistance \( \Omega \) for each CT ratio: | **CT ratio** | **Secondary resistance \( \Omega \)** | |--------------|----------------------| | 50:5 | 0.061 | | 100:5 | 0.082 | | 150:5 | 0.104 | | 200:5 | 0.125 | | 250:5 | 0.146 | | 300:5 | 0.168 | | 400:5 | 0.211 | | 450:5 | 0.230 | | 500:5 | 0.242 | | 600:5 | 0.296 | Understanding this graph and table is crucial for analyzing the performance and compatibility of CTs with different relay settings.
Transcribed Image Text:**CO-8 Relay and CT Analysis** A CO-8 relay with a current tap setting of 5 amperes is used with a 100:5 current transformer (CT). The CT secondary current \( I' \) serves as the input to the relay operating coil. The CO-8 relay burden for various relay input currents is listed in the table below: | **CO-8 relay input current \( I' \), A** | 5 | 8 | 10 | 13 | 15 | |-----------------------------------------|----|----|----|----|----| | **CO-8 relay burden \( Z_B, \, \Omega \)** | 0.5| 0.8| 1.0| 1.3| 1.5| The graph represents the relationship between the secondary exciting voltage \( E' \) and the exciting current \( I_e \) for the CT. **Graph Explanation:** - **X-axis:** Represents the exciting current, \( I_e \). - **Y-axis:** Represents the secondary exciting voltage, \( E' \). - Multiple curves depict different CT ratios ranging from 50:5 to 600:5. The table next to the graph provides the secondary resistance \( \Omega \) for each CT ratio: | **CT ratio** | **Secondary resistance \( \Omega \)** | |--------------|----------------------| | 50:5 | 0.061 | | 100:5 | 0.082 | | 150:5 | 0.104 | | 200:5 | 0.125 | | 250:5 | 0.146 | | 300:5 | 0.168 | | 400:5 | 0.211 | | 450:5 | 0.230 | | 500:5 | 0.242 | | 600:5 | 0.296 | Understanding this graph and table is crucial for analyzing the performance and compatibility of CTs with different relay settings.
### Electrical Engineering Problem Analysis #### Graph Explanation: The graph presents the relationship between secondary exciting current (Iₑ) on a logarithmic x-axis and secondary voltage (V) on a logarithmic y-axis. Various lines represent different current transformer (CT) ratios, such as 100:5, 150:5, 200:5, etc. #### Problem Statement: 1. **Primary Current Computation:** - Compute the primary current for two scenarios: - (a) \( I' = 10 \, \text{A} \) and \( Z_B = 1 \, \Omega \) - (b) \( I' = 13 \, \text{A} \) and \( Z_B = 1.3 \, \Omega \) 2. **Plotting Task:** - Plot \( I' \) versus \( I \) for five values of \( I' \) detailed in a provided table. - Previously calculated primary currents for \( I' = 5, 8, \) and \( 15 \, \text{A} \) during Session 12 (October 2nd). - Ensure the plot clearly shows the saturation region of the curve. 3. **Reliable Relay Operation:** - For trustworthy relay operation, ensure the fault-to-pickup current ratio with minimum fault current exceeds two. - Determine the minimum fault current for employing this CT and relay with a 5-A tap setting. - In essence, calculate the minimum fault current necessary for the relay to trip reliably. This exercise involves analyzing physical electrical principles associated with CTs and relay settings, requiring understanding of saturation curves and fault current calculations for effective power system protection.
Transcribed Image Text:### Electrical Engineering Problem Analysis #### Graph Explanation: The graph presents the relationship between secondary exciting current (Iₑ) on a logarithmic x-axis and secondary voltage (V) on a logarithmic y-axis. Various lines represent different current transformer (CT) ratios, such as 100:5, 150:5, 200:5, etc. #### Problem Statement: 1. **Primary Current Computation:** - Compute the primary current for two scenarios: - (a) \( I' = 10 \, \text{A} \) and \( Z_B = 1 \, \Omega \) - (b) \( I' = 13 \, \text{A} \) and \( Z_B = 1.3 \, \Omega \) 2. **Plotting Task:** - Plot \( I' \) versus \( I \) for five values of \( I' \) detailed in a provided table. - Previously calculated primary currents for \( I' = 5, 8, \) and \( 15 \, \text{A} \) during Session 12 (October 2nd). - Ensure the plot clearly shows the saturation region of the curve. 3. **Reliable Relay Operation:** - For trustworthy relay operation, ensure the fault-to-pickup current ratio with minimum fault current exceeds two. - Determine the minimum fault current for employing this CT and relay with a 5-A tap setting. - In essence, calculate the minimum fault current necessary for the relay to trip reliably. This exercise involves analyzing physical electrical principles associated with CTs and relay settings, requiring understanding of saturation curves and fault current calculations for effective power system protection.
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