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Expert Speaks | October 2016

We select equipment which abides by latest norms during design stage

Ashish Gupta, Head - Power Management Group (PMG), TECHPORT Regional Manufacturing Support Organisation (RMSO), Holcim - South Asia Region.

What are the power quality (QoP) issues you face in your day-to-day operations and how do you handle them (including through internal team or a service provider)?
Power Quality can be defined as a power problem manifested in voltage, current, or frequency deviations that results in failure or misoperation of customer equipment. The following are power quality issues being faced by us:
1. Transients: It is a sudden, non-power frequency change in the steady-state condition of voltage, current, or both. The most common causes are lightning, capacitor switching, cable charging, etc.
2. Long duration voltage variations: Long-duration variations can be either over-voltages, under-voltages and sustained interruptions. Over-voltages and under-voltages generally are not the result of system faults, but are caused by load variations on the system, system switching, etc. When the supply voltage has been zero for a period of time in excess of one minute, the long-duration voltage variation is considered a sustained interruption. Voltage interruptions longer than one minute are often permanent and require human intervention to repair the system for restoration.
3. Short-Duration Voltage Variations: It is what we usually refer to as voltage dip. Short-duration voltage variations are caused by fault conditions, the energisation of large loads which require high starting currents, or intermittent loose connections in power wiring. Depending on the fault location and the system conditions, the fault can cause either temporary voltage drops (sags), voltage rises (swells), or a complete loss of voltage (interruptions).
4. Voltage Imbalance: The primary source of voltage unbalances of less than two per cent is single-phase loads on a three-phase circuit. Voltage unbalance can also be the result of blown fuses in one phase of a three-phase capacitor bank. Severe voltage unbalance (greater than five per cent) can result from single-phasing conditions.
5. Waveform Distortion: Waveform distortion is defined as a steady-state deviation from an ideal sine wave of power frequency principally characterized by the spectral content of the deviation. The most primary cause are harmonics - i.e. voltages and currents in an electric power system are a result of non-linear electric loads.
6. Voltage Fluctuation: Loads that can exhibit continuous, rapid variations in the load current magnitude can cause voltage variations that are often referred to as flicker. This is caused by an arc furnace, which is one of the most common causes of voltage fluctuations experienced on utility transmission and distribution systems.
7. Power Frequency Variations: Power frequency variations are defined as the deviation of the power system fundamental frequency from it specified nominal value of 50 Hz.

Initially while setting up of a new plant/factory or while procuring a new equipment we take care during design stage to select equipment which abides by the latest IEC/IEEE/IS norms and other technical parameters so that most efficient equipment is procured. In operational plant the above parameters are monitored by plant level and also specialised operational support teams.

What are the power quality equipment you use to monitor and mitigate the problems and please narrate their uses?
We use three phase and single phase power quality meters and precision power quality analysers for measuring and monitoring parameters as voltage, current, active power, reactive power, apparent power, power factor, frequency, current flowing on the neutral line (only on 3 phase 4 wire measurement), active power energy, reactive power energy, apparent power energy, demand measurement, etc. The makes are Fluke and Kyoritsu.

In an ideal situation what kind of QoP supplies do you expect from the distribution companies and what are the inadequacies you are facing now?
A quality electrical power supply must be available at all times, always within range of the frequency and magnitude tolerance limits, and with a perfectly sinusoidal waveform. A reliable, efficient and safe power supply is essential for guaranteeing productivity and lowering energy cost. We presently experience frequency and voltage variations, power cuts, and load-sheddings very often.

What are the measures that may be taken to improve the power supply scenario?
We can install active or passive filters, harmonic compensators, emergency generators or UPS systems, or can intervene directly on the system structure (i.e. through transformers, new distribution lines, etc.).

How do you think the power supply scenario compares with advanced countries in terms of QoP?
The power supply scenario in India, especially when compared to advanced countries is relatively poor. The basic cause of deteriorating quality of power supply in India is the widening gap between demand and supply. Frequent power cuts, inadequate transmission and distribution systems, regular breakdowns and load shedding, theft of power, lack of service culture, low and high frequency regime in the power grid for about 60 per cent of the time during the year, fluctutaions such as situations where a 220 kV system voltage goes to 165 kV and 400 V system goes below 300 V, besides harmonic levels sometimes touching 22 per cent, are the reasons. Total Harmonic Disturbances (THD) are responsible for losses, system maloperation or damage to consumer equipment in India.

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