Businesses with significant electrical loads often review reactive energy when looking for avoidable network charges and inefficient use of connection capacity. Reactive power is an essential part of many alternating-current systems, but excessive or poorly controlled reactive energy can increase current flow and lead to additional charges under the applicable tariff and supply agreement.
Reactive power compensation is used to manage that balance. Its financial effect must be calculated from actual measurements, bills, the current operator tariff and the characteristics of the installation.
What is reactive power?
Three power quantities are commonly distinguished in AC systems:
- active power (P) — power converted into useful work or energy, such as driving machinery,
- reactive power (Q) — power associated with electric and magnetic fields in equipment,
- apparent power (S) — the combined effect of active and reactive power on the electrical system.
Reactive power is not simply “wasted energy”. It is inherent in the operation of many motors, transformers, power supplies and other loads. The issue arises when the reactive-energy profile exceeds contractual or tariff conditions or causes unnecessary loading of the installation.
Why is reactive power compensated?
An excessive reactive component can contribute to:
- higher current for the same active-power demand,
- additional loading of cables, transformers and switchgear,
- greater network losses,
- reduced available capacity in parts of the installation,
- reactive-energy charges where the tariff and agreement provide for them.
In Poland, reactive-energy settlements depend on the applicable regulations, the distribution-system operator’s approved tariff and the customer’s agreement. Charges may apply to excess inductive reactive energy and to capacitive reactive energy under the conditions defined in those documents. They should be checked against the current bill rather than assumed from a general rule.
How does reactive power compensation work?
The compensation system is selected to counter the reactive-power characteristic of the installation:
- capacitor banks are commonly used to compensate inductive loads,
- reactors can be used where capacitive reactive power needs to be controlled.
The design may also need to consider load variability, harmonics, switching steps, resonance risk and the location of the compensation equipment. An incorrectly selected system can overcompensate or interact adversely with the installation.
Figure 1. Capacitor bank.
Figure 2. Capacitor and reactor bank.
What does an implementation process involve?
Selecting a compensation system normally requires:
- measurements and analysis to identify the type, magnitude and variability of reactive power,
- review of bills, the supply agreement and the current tariff,
- selection of a compensation method suited to the loads and technical constraints,
- calculation of the required rating and switching stages,
- assessment of harmonics and resonance risk where relevant,
- design, implementation and post-installation verification.
How are reactive-energy charges calculated?
The amount charged depends on factors including:
- the customer’s supply and distribution agreements,
- the tariff group and the operator’s approved tariff,
- measured active and reactive energy during the billing period,
- the contractual power-factor limit,
- the relevant price and multiplier defined by the current settlement rules.
The Polish tariff regulation defines settlement principles and formulas, but the actual parameters and prices must be read from the current tariff and agreement. The illustration below is retained from the source article as an example; it must be checked against the version of the rules applicable when an analysis is prepared.
Which facilities may benefit from an assessment?
Reactive-power analysis is commonly relevant to:
- manufacturing plants,
- shopping centres,
- office buildings and large service facilities,
- installations with extensive HVAC, automation, power electronics or distributed generation.
Whether compensation is technically and financially justified depends on the measured load profile and current billing conditions.
Potential benefits of correctly selected compensation
Depending on the installation, the benefits can include:
- reduced reactive-energy charges,
- lower current and losses in parts of the installation,
- release of usable capacity,
- improved power-factor control.
These outcomes are not automatic. They depend on correct measurement, design, settings and subsequent verification.
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TERMOCENT supports clients in assessing the energy performance and technical condition of buildings and installations.
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TERMOCENT can prepare a measurement-based analysis and propose a solution matched to the installation and billing conditions.
