Please enable JavaScript.
Coggle requires JavaScript to display documents.
Other PQ Problems (G1 (Voltage Unbalanced (Causes (1.Malfunctioning of…
Other PQ Problems
G1
-
Mitigation
1. For the Utility
- Repairing Malfunction equipment or redistributing loads
2. For The End Users
- Proper Testing & Communication with the Utility
- Adjustable Speed drives with AC Lines & DC Link Reactors
- Motor can be derated to reduce the damages.
- Voltage Regulator
Standards
1. ANSI C84.1
- Maximum Voltage unbalance Limit to 3% under no load condition
2. National Equipment Manufacturer Association (NEMA)
- Voltage Unbalance Limit to 1% per NEMA MG-1
Causes
1.Malfunctioning of Equipment
- Blown Capacitor Fuses
- Open Delta Regulator
- Open Delta Transformer
-
-
-
-
6. Irregular Impedance bet phases in the motor
- Defect in Power Circuit Connection
- The Motor Contacts rotor and stator windings
-
-
-
-
G4
Definition:
Transients are power quality disturbances that involves a destructive high magnitude of current and voltage or even both. It may reach thousands of volts and amps even in low voltage system :
Effect
1- Elecronic Equipment
- Improper specification and installation of TVSS can aggravate the failures.
2- Motors
Transients will make motors run at higher temperatures.3- Electrical equipment
Transients degrade the contacting surfaces of circuit breakers and switches.
Mitigation:
Damages due to such PQ problems are uncommon as compared to voltage sags and interupption, end -users may use. Transient Voltage Surge Suppresoor (TVSS), while utilitiesinstall surge arresters.
causes of transient
switching activity
- switching of power lines
-switching load on or off
-capacitor bank switching
- reclosing operations
- tap changing on transformers
Frequency Variation
Power frequency variation involves a change in frequency from the normally stable utility frequency of 50 or 60Hz, depending on geographic location
Causes:
Causes by erratic operation of emergency generators or unstable frequency power sources.
Effects:
May confuse logic systems and effect the operating speed of rotating machinery
Monitoring:
The frequency of supply is to be maintained within 1.5% of 50 Hz, except for momentary fluctuations.
To minimize frequency excursions the generation must be matched to loading and losses.
G2
- Long Duration Variation
Definition: RMS value deviation at power frequency for more than 1 minute
Undervoltage
-
Definition
IEEE-1159 - Decrease in the AC voltage (RMS), 0.8-09xUn, more than 1 minute
-
Overvoltage
Classification
-
-
General Cause
- Capacitor switching
- Load shedding of the neighboring distribution system
- Mis-setting of voltage tap on transformer
Mitigation
- Adjust transformer to the correct tap setting
- Install voltage regulator/automatic on-load tap changer to improve voltage profile
- Manually or automatically switching off excess capacitor banks during light load or peak hour
Definition - Increase in AC voltage in RMS, 1.1-1.2 p.u. >1min
IEC-60071-1 - Any voltage between 1-phase conductor and earth or between phase conductors having a peak value exceeding the corresponding peak of the highest voltage.
Sustained Interruption
- Magnitude and duration:
- Short Interruption - Less than 0.1 p.u. and half-cycle to 1 minute
- Sustained Interruption - 0 p.u., more than 1 minute
-
-
-
G3
- Voltage Fluctuation and Flickers
Voltage Fluctuation
-
-
Definition
A systematic variations of the voltage waveform envelope, or a series of random voltage changes (IEEE, ANSI C84.1)
-
-
-
-
-
-
