Lab_1_Voltage_Sags_and_Harmonics

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British Columbia Institute of Technology *

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3130

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Electrical Engineering

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Apr 3, 2024

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Lab 1 Voltage Sags and Harmonics Objectives To Understand the fundamentals of voltage sags and harmonics, and their impacts on power systems Part A – Voltage Sags Analysis Introductions Part A of the report explains the impact of voltage sags on the mills, and the reason their equipment has been tripped offline. In this file, I Have attached a Single line diagram as in Figure 1. Single line diagram Figure 1Final Single Line Diagram

Using Load Flow Analysis Figure 2 Load Flow Analysis SLD Power in W Q in Var BCH-WSN 28543 28166 T1 2285 -1267 T2 29984 24401 Generator 32000 17175 Figure 3 Results of Load Flow Analysis As we can see in Figure 3 the results matched the required values of a. BC Hydro Williston Substation b. Transformers T1, T2, and Generator

Short Circuit Analysis test in this test we be testing faults across a. Remote Bus b. BCC bus c. CRD bus d. Neighboring Plant bus e. Load flow analysis with Neighboring-XFMR while it is energized Bus Voltage (% of nominal) Bolted Fault or Disturbance Location Bus A Bus B MCC-A MCC-B Remote Fault 96.7% 93.89% 96.66% 93.89% BCC66 Bus 72.12% 57.85% 72.12% 57.85% CRD66 Bus 66.76% 49.39% 66.76% 49.97% Neighboring Bus 94.52% 90.76% 94.52% 90.76% Transformer energization 67.27% 54.88% 67.27% 54.88% Figure 4 Results of Short Circuit Test Figure 5 Example of short circuit Test on Neighboring bus

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Figure 6 Fault at Remote bus Figure 7Fault at BCC Bus

Figure 8 Fault at CRD Bus Figure 9 Load Analysis with Load energized.

Discussion and analysis ANS: As the MCC Bus voltage drops, the Control voltage also drops. 2. Review the provided contactor technical specification (Eaton) and determine its drop-out voltage. When the contactor drops out, it means that the motor will stop, and the associated process will stop. ANS: As in Page 3 table 2: Ratings the drop out voltage is 60% Rated Coil Voltage and the rated voltage is 7.2kV. Drop-out voltage = 0.6 * 7.2kV = 4.32kV 3. The motors in MCC A and B drive critical steam processes and are controlled by these Eaton contactors. Based on the determined drop-out voltage, determine whether process interruption is expected for faults at various locations. Highlight the results in the table in red if interruption to operation is likely. ANS: Yellow Highlight = will drop out, Red Highlight = will not drop out Bus Voltage (% of nominal) Bolted Fault or Disturbance Location Bus A Bus B MCC-A MCC-B Remote Fault 96.7% 93.89% 96.66% 93.89% BCC66 Bus 72.12% 57.85% 72.12% 57.85% CRD66 Bus 66.76% 49.39% 66.76% 49.97% Neighboring Bus 94.52% 90.76% 94.52% 90.76% Transformer energization 67.27% 54.88% 67.27% 54.88% 4. Repeat #2 but for transformer energization in-rush at a neighboring facility. (Results from Step4) ANS: Done in previous Question.

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5. The contactor-in-question can ride-through a voltage sag down to its drop-out voltage for 3 cycles. Assuming theBC Hydro breakers at Canreed and Williston carry a 3-cycle opening time, does your conclusion change in #3? Why or why not? ANS: no it does not, as the minimum trip time is 1.5 cycles found in the datasheet. So since 3 cycles is more than 1.5, it will pick up and drop out any voltages above 60% 6.What is the reason behind differences in magnitude of voltage sags? ANS: because it depends on fault location, system impedance and how long the fault is. 7.Is there any difference in voltage sags between Bus A and B for faults at the same location? Why? ANS: yes because Bus A has a generator connected to it which causes the differences. 8.What other equipment in the mill may be sensitive to voltage sags? (Hints: recall what you’ve learnt from the very first lecture of Elex 3402) ANS: VFDs and electronic and industrial equipment. 9.What conclusions can be made? a. What are the most likely causes of interruption to the mill process? b. Which bus/buses is/are more vulnerable and why? c. Without modifying the mill’s or BC Hydro’s power system, is there anything that the Mill can do to avoid the interruptions as identified above? ANS: After analysing the results I found that Remote Bus, Neighboring bus had an average bus voltage of (90%-95%) while the BCC66 and CRD66 bus had an average bus voltage of (60%-70%) of Nominal. a. The most likely causes of interruption to the mill process could include power outages, voltage sags or surges, equipment failures or malfunctions, and human error. These interruptions could be caused by factors such as severe weather, equipment maintenance or repair, load changes, or operator error. b. The BCC66 and CRD66 and the Transformer Energization Busses because they are more prone to voltage sag. c. Scheduled maintenance plan for the whole system as well as monitoring systems that detect faults and trips.

Part B – Preliminary Harmonic Analysis Introduction This part of the report will include an estimate to see if the utility requirements based on the IEEE 519 Standard are met based on the preliminary design. Single line Diagram Figure 10 Processing Plant SLD Load flow Current on Main Cable Motor FLA = HP ∗ 746 √ ( 3 ) ∗ Vl ∗ n ∗ PF = 193.26 Total Current = 210.52 * 2 = 386.52 Fault current and Current Ratio Calculation Zbase ¿ Vbase 2 s = 0.36 Ω Z = Zpu * Zbase = 0.36 * 0.0575 = 0.0207

Isc = V/Z = 600/ 0.0207 = 28.986 kA Ratio = Isc/ Total current = 28986/386.52 = 74.99 Voltage Distortion Limits Since the voltage is 600V which is less than 1kv we use individual harmonic = 5% Total Harmonic Distortion THD = 8% Current Distortion Limits Since the ratio is 74.99 which is around 75 we use Current Harmonic Spectrum Calculations Using a rated FLA of 386.52 and TDD of 12% so the fundamental = Total Current* %fundamental current( 1 – TDD) Figure 11 Harmonic Current

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Cable & Transformer Impedances W = 2*pi*f , L= XL/2*pi*f = 0.239mH/Km , X= W*h*L Sample reactance calculation for 1 st order harmonic = 377*1*0.239 / 1000 = 0.0901 H / Km Z = sqrt(R^2 + X^2) LT= 0.1503 mH

Harmonic Voltage VH= IH * ( Zcable + Z transformer) Items which don’t comply with Alabama Power’s requirements (IEEE 519) The items that don’t comply will be highlighted in red

Questions and Analysis 14. If only one of the VFDs is online, does it change the voltage and current TDD and THD at the MCC? Please record the changes, if applicable, and describe whether it changes the status of compliance of the MCC bus. It does not change, since the TDD and THD are ratios of Voltage and current, so if it is only 1 the voltage and current values would be halved but the ratios would not change. 15. If the plant decides to add an equivalent amount (in terms of Amps) of motor loads, which doesn’t carry any harmonics, does it change your conclusion in #3? Why/Why not? Yes it would cause a smaller percentage, because the ratio is divided by a larger number. 16. What is the effect on voltage and harmonic current distortion (%) by using a longer or shorter cable? Shorter cable THD will Increase because there is less inductance, with a longer cable it have a decreased THD with more inductance. 17. What is the effect on voltage and harmonic current distortion (%) by using a larger or smaller transformer impedance (%Z)? a larger transformer impedance can result in a low frequency harmonic and an increase in high frequency harmonics. A smaller transformer impedance will have the opposite effect. 18. Why does IEEE 519 uses TDD for current distortion and not THD Because TDD is more accurate for measuring Harmonic Distortion cause by PF< 1.

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