1. Basic Difference Between Harmonics and Surge
|
division |
Harmonics |
Surge |
|
definition |
Caused by nonlinear loads in AC power |
Occurs within a very short period of time (nanoseconds to microseconds) |
|
Voltage/current waveform having a frequency that is an integer multiple of the fundamental wave |
High voltage/high current impulses, momentary transients |
|
|
cause |
Power conversion devices (inverters, rectifiers), power electronic devices, etc. |
Lightning, switch operation, large load shedding, induction, etc. |
|
influence |
Equipment damage, overheating, power loss, malfunction, communication failure |
Insulation breakdown, precision equipment failure, malfunction, damage to communication/control devices |
|
Waveform characteristics |
A regular and periodic waveform (usually 3rd, 5th, etc.) |
Abnormal, non-periodic and very short-lived |
|
Frequency |
Integer multiples of 60Hz (fundamental wave) (120Hz, 180Hz, etc.) |
Very wide bandwidth (several kHz to several tens MHz), typical high-frequency impulse type |
|
Continuous/occurring |
Existing in the system for a long time or continuously |
Instantaneous (μs~ns), irregular |
2. Key technical criteria
(1) Harmonic technology standards
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Domestic standards
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Korea Electric Power Corporation Basic Electricity Supply Terms and Conditions Enforcement Rules, Electric Safety Management Act, KDS 31 60 10, etc. apply
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Voltage harmonic distortion (THD) in distribution system : 5% or less
-
Apply individual harmonic voltage ratio criteria by major order (e.g. 5th, 7th, 11th, etc.)
-
Differential application: 3.0% for 66kV or below, 1.5% for 69kV~161kV, 1.0% for 161kV or above
-
Mandatory installation of protective devices (filters, reactors, etc.) when the allowable standard is exceeded
2. International standards
-
IEEE Std. 519-2014 (USA):
-
Voltage THD (total harmonic distortion) 5% or less (less than 69kV), individual standards by harmonic order
-
Current THD (total current distortion) is measured based on various criteria 3 depending on load conditions.
(2) Surge technology standards
-
Technical definition and applicable standards
Surge is a transient voltage/current that occurs momentarily and is regulated by the IEC 61643 series (international standard for SPD) and the SPD installation guidelines of the Korea Occupational Safety and Health Agency.
The purpose of a surge protective device (SPD) is to limit transient overvoltage and disperse/block surge current.
-
Test and Performance
Main standards: IEC 61643-11, 61643-31 (for PV/DC), 61643-41 (for ESS)
Lightning impulse (based on 1.2/50μs, 8/20μs), maximum allowable current, etc.
SPD is evaluated based on installation location (zone), protection level, test waveform, leakage current, and environmental resistance.
3. Summary
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Harmonics exist for a long time and have periodic, long-term adverse effects on the facility, so strict management standards for THD and order are required.
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Surge is an extremely momentary but high-energy transient phenomenon, so SPD installation and performance testing according to international standards are essential to protect electronic devices.
-
Since both phenomena cause direct and indirect facility damage, it is important to take preventive measures and maintain facilities in accordance with technical standards.
|
division |
Application criteria |
Voltage reference (THD) |
Test/Installation Standards |
|
Harmonics |
IEEE 519, KDS, etc. |
5% or less (low pressure standard) |
Filters, Reactors, Quality Analyzers |
|
bibliography |
IEC 61643 etc. |
Short impulses (8/20 μs, etc.) |
SPD, Lightning Arrestor |
It is recommended to check in advance whether each facility complies with the harmonic and surge management standards, and to apply protective devices and monitoring/analysis systems that are suitable for the on-site conditions.
Surgefree