Voltage sags and Interruptions

download Voltage sags and Interruptions

of 66

  • date post

    04-Apr-2018
  • Category

    Documents

  • view

    222
  • download

    2

Embed Size (px)

Transcript of Voltage sags and Interruptions

  • 7/30/2019 Voltage sags and Interruptions

    1/66

    Voltage Sags and InterruptionsVoltage Sags and InterruptionsVoltage Sags and InterruptionsVoltage Sags and Interruptions

    1 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    2/66

    Voltage sags and interruptions are related power qualityproblems. Both are usually the result offaults in the power

    system and switching actions to isolate the faulted sections.

    They are characterized by rms voltage variations outside thenormal operating range of voltages.

    Sag :If the RMS Voltage is below the nominal voltage

    by 10% to 90% for 0.5 Cycles to 1 Min.

    2 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    3/66

    Sag and InterruptionsSag and InterruptionsSag and InterruptionsSag and Interruptions

    A voltage sag is a short-duration (typically 0.5 to 30 cycles)reduction in RMS voltage caused by faults on the power

    system and the starting oflarge loads,such as motors.

    Momentary interruptions (typically not more than 2 to 5 s)cause a complete loss of voltage and are a common result of

    the actions taken by utilities to clear transient faults ontheir systems. Sustained interruptions of longer than 1 minare generally due to permanent faults.

    3 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    4/66

    Fault locations on the utility powerFault locations on the utility powerFault locations on the utility powerFault locations on the utility power

    systemsystemsystemsystem

    5 or 6 cycles for the breaker to operate.

    Remains open for12 cycles up to 5 s

    4 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    5/66

    Example of fault locations that caused misoperation of sensitive production equipmentat an industrial facility (the example system had multiple overhead distribution

    feeders and an extensive overhead transmission system supplying the substation).

    5 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    6/66

    Voltage sag due to a shortVoltage sag due to a shortVoltage sag due to a shortVoltage sag due to a short----circuit faultcircuit faultcircuit faultcircuit fault

    on a parallel utility feederon a parallel utility feederon a parallel utility feederon a parallel utility feeder

    Characteristic measured at a customer location on an

    unfaulted part of the feeder6 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    7/66

    Utility shortUtility shortUtility shortUtility short----circuit fault event with two fast tripcircuit fault event with two fast tripcircuit fault event with two fast tripcircuit fault event with two fast trip

    operations of utility line recloser.operations of utility line recloser.operations of utility line recloser.operations of utility line recloser.

    Momentary interruption (actually two separateinterruptions) observed downline from the fault

    7 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    8/66

    Estimating Voltage Sag PerformanceEstimating Voltage Sag PerformanceEstimating Voltage Sag PerformanceEstimating Voltage Sag Performance 1. Determine the number and characteristics of voltage sags that

    result from transmission system faults.

    2. Determine the number and characteristics of voltage sags thatresult from distribution system faults (for facilities that are suppliedfrom distribution systems).

    3. Determine the equipment sensitivity to voltage sags. This will

    determine the actual performance of the production processbased on voltage sag performance calculated in steps 1 and 2.

    4. Evaluate the economics of different solutions that could improve theperformance, either on the supply system (fewer voltage sags) or within

    the customer facility (better immunity).

    8 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    9/66

    Area of vulnerabilityArea of vulnerabilityArea of vulnerabilityArea of vulnerability

    The likelihood of sensitive equipment being subjected to voltage

    lower than its minimum voltage sag ride-through capability.

    Voltage sag ride-through capability- Minimum voltagemagnitude a piece of equipment can withstand or tolerate without

    misoperation or failure. (Equipment voltage sag immunity or

    susceptibility limit.) Area of vulnerability is determined by the total circuit miles of

    exposure to faults that can cause voltage magnitudes at an end-user

    facility to drop below the equipment minimum voltage sag ride-through capability.

    9 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    10/66

    Illustration of an Area of VulnerabilityIllustration of an Area of VulnerabilityIllustration of an Area of VulnerabilityIllustration of an Area of Vulnerability

    10 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    11/66

    EXISTING VOLTAGE DIP IMMUNITY TESTINGEXISTING VOLTAGE DIP IMMUNITY TESTINGEXISTING VOLTAGE DIP IMMUNITY TESTINGEXISTING VOLTAGE DIP IMMUNITY TESTING

    STANDARDSSTANDARDSSTANDARDSSTANDARDS Existing standards for testing equipment voltage dip immunity focus primarily on verifying a minimum

    immunity requirement for equipment response to voltage dips. IEC Standard 61000-4-11 [3] is for

    equipment below 16 amps. Usually, these will be single phase devices where the testing is fairly

    straightforward because multiple phase dips are not an issue and phase shift is usually of secondary

    importance. The most important consideration in this case is the actual immunity characteristic that isrequired. The immunity test levels from 61000-4-11 and 61000-4-34 are compared with the immunity

    requirements from SEMI F-47 in Figure 1.

    Figure 1. Immunity testing levels from IEC 61000-4-11 and 61000-4-34 compared with immunity requirements in SEMI F47.11 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    12/66

    Testing three phase equipment is more complicated. Both IEC 61000-4-11 [3] and

    IEC 61000-4-34 [4] cover single-phase and three-phase equipment in a similar way, butthe former only applies to equipment up to 16A per phase, whereas the latter covers

    larger equipment.

    Figure 2a. Vectors recommended by IEC [3] [4] for phase-to-neutral testing of three-phase equipment.

    Figure 2b. Vectors recommended by IEC [3][4] for phase-to-phase testing of three-phase equipment. Note that the vectors

    in method A are preferred, the vectors in method B are

    acceptable, and the vectors in method C are not acceptable.12 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    13/66

    An Adjustable Speed Drive (ASD) is selected as an example industrial loadfor testing because it is very common in many industrial facilities, is often part

    ofprocesses sensitive to voltage dips, and is a three phase load that illustratesthe importance of the voltage dip characteristics on the device immunity.

    During a voltage dip or momentary interruption, the diodes in an ASD rectifierbridge will not conduct if the peak line voltage drops below the dc busvoltage. While the ASD is still controlling the motor and its load, energy isdrawn from the dc-bus capacitors, which will cause the dc-bus voltage to

    decrease. If the dc-bus voltage falls below the ASDs undervoltage trippoint before the line voltage returns, then the control circuit will respondaccording to the drives program, typically shutting down the drive

    ASD Performance to SAGASD Performance to SAGASD Performance to SAGASD Performance to SAG

    13 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    14/66

    Basic diagram of the power section of transistorizedadjustable-speed drive, including PWM ac and BLDC.

    14 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    15/66

    ASDASDASDASD

    A typical 5 hp (3.5 kW) ASD is used, tests were conducted to determine how the drive would

    respond to voltage dips that were generated using different test methods. The tests were

    conducted with the drive loaded to 81 percent of full load, with an input voltage of400V

    rms phase-to-phase, 50 Hz. The voltage sag generator used is compatible with SEMI F47-

    0200, SEMI F42-0200, and the proposed IEC 61000-4-34 standards.

    Figure. ASD voltage dip immunity testing setup.

    15 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    16/66

    Minimum dc bus values during the voltage dipMinimum dc bus values during the voltage dipMinimum dc bus values during the voltage dipMinimum dc bus values during the voltage diptests (refer to Table 1 for test conditions).tests (refer to Table 1 for test conditions).tests (refer to Table 1 for test conditions).tests (refer to Table 1 for test conditions).

    16 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    17/66

    Results of ASD voltage dip immunity testing withResults of ASD voltage dip immunity testing withResults of ASD voltage dip immunity testing withResults of ASD voltage dip immunity testing with

    different voltage dip characteristics.different voltage dip characteristics.different voltage dip characteristics.different voltage dip characteristics.

    17 M.SURESH AP/EEE/KEC/PERUNDURAI

  • 7/30/2019 Voltage sags and Interruptions

    18/66

    Equipment sensitivity to voltage sagsEquipment sensitivity t