Measuring and analyzing power quality is one of the important analyses to evaluate the quality of power supply indicators such as voltage, current, power factor, frequency, in order to detect early abnormalities of power quality such as overvoltage/undervoltage, high harmonic distortion, voltage imbalance, overload, etc., which directly affect the production process, operation and life of the equipment used. From the analysis results, power system operators can come up with solutions and select equipment to improve power quality.
1. Collected parameters:
Measure the total harmonic distortion of voltage and current (%THD) or harmonic distortion for individual harmonics from order 1 to order 51. Determine the total harmonic distortion of current according to the maximum load current (%TDD).
Measure and determine operating voltage, frequency, check for undervoltage, overvoltage, voltage imbalance, voltage flicker, voltage drop, frequency deviation. Check voltage and frequency when starting large motors or sudden load changes.
Measure and determine load current, power factor, power loss. Measure active power such as active power, reactive power, consumed electric energy and operating efficiency.
Collected power quality parameters include:
♦ Harmonics
– Individual harmonic order
– Total current harmonic distortion (TDD)
– Total voltage harmonic distortion (THD)
♦ Voltage
– Operating voltage
– Voltage deviation
– Voltage flicker
– Voltage dip
♦ Frequency
– Operating frequency
– Frequency deviation
♦ Current
– Steady operating current
– Low load current
– High load current
– Motor starting current
♦ Power factor
♦ Energy loss
♦ Operating power
– Reactive power
–Active power
♦ Equipment efficiency
♦ Phase balance
– Negative sequence voltage
2. Measuring equipment:
3. Applicable standards:
♦ Circular No. 39/2015/TT-BCT: Regulations on power distribution systems
♦ Circular No. 30/2019/TT-BCT: Amending and supplementing a number of articles of Circular No. 25/2016/TT-BCT and Circular No. 30/2019/TT/BCT
♦ Circular No. 25/2016/TT-BCT: Regulations on power transmission systems
♦ Circular No. 42/2015/TT-BCT: Regulations on power metering in power systems
♦ QCVN: 2015/BCT: National technical regulations on electrical engineering
♦ IEEE 519 2014: IEEE standard for harmonic control in electric power systems