02 Sep, 2026
I. Selection of Shunt Reactors
Source: Transmission & Distribution Equipment Network. For local small power systems, the shunt-reactor capacity is determined after calculating and analyzing power-frequency voltage rise and generator self-excitation, and then considering the actual conditions of the small power system. The recommended value can be preliminarily calculated using the formula shown in the original document. Source: http://tede.cn
Please visit the Transmission & Distribution Equipment Network for more information.
For a line voltage of 110–220 kV and a line length below 300 km, use 0.4–0.45. For a line voltage of 330 kV and a line length above 300 km, 0.5 may be used.
Source: http://tede.cn
Ue — rated line voltage of the power network (kV). Source: http://tede.cn
Ic — capacitive current of the power network (kA). Source: http://tede.cn
This value can be obtained by calculation or direct measurement. If the susceptance of the transmission line can be found in a relevant handbook, it can be calculated directly using the formula shown in the original document. Please visit the Transmission & Distribution Equipment Network for more information.
After calculating the shunt-reactor capacity using the above formula, standardize the result and select the reactor. The number of units depends on the total shunt-reactor capacity. For a design capacity above 10,000 kvar and infrequent switching, one centrally installed compensation unit can be selected. For capacities below 8,000 kvar in small power systems with lower voltage levels, two distributed compensation units are generally selected to facilitate operational adjustment.
Small power systems have lower compensation capacities and voltage levels and may use distributed outdoor installation. For flexible operation, adjustment and switching, a ZN-type vacuum circuit-breaker switchgear cabinet may be used.
II. Selection of Series Reactors
1. When the reactor is used only to limit inrush current, a reactance rate of 1% is recommended.
2. When grid harmonics are mainly the 3rd order and above and the 3rd-harmonic content is relatively small, a 0.5%–1% series reactor may be selected. However, it is necessary to verify whether 3rd-harmonic amplification after capacitor energization exceeds or approaches the limit, with an appropriate safety margin.
3. When grid harmonics are mainly the 3rd order and above and the 3rd-harmonic content is relatively large and has already exceeded or approached the limit, a mixed installation of 12% and 4.5%–6% series reactors may be selected.
4. When the 3rd and 5th harmonics are dominant, with relatively low 3rd-harmonic content and relatively high 5th-harmonic content, select a 4.5%–6% series reactor and avoid using 0.1%–1% series reactors where possible.
5. When the 3rd and 5th harmonics are dominant, with slightly higher 3rd-harmonic content and relatively low 5th-harmonic content, select a 0.1%–1% series reactor. However, verify whether 3rd-harmonic amplification after capacitor energization exceeds or approaches the limit, with an appropriate margin.
6. When grid harmonics are mainly the 5th order and above and the 5th-harmonic content is relatively small, a 4.5%–6% series reactor should be selected.
7. When grid harmonics are mainly the 5th order and above and the 5th-harmonic content is relatively large, a 4.5% series reactor should be selected. For 0.1%–1% series reactors, serious amplification or resonance of the 5th and 7th harmonics must be prevented. For 4.5%–6% series reactors, serious amplification or resonance of the 3rd harmonic must be prevented.
8. When the system has no harmonic source, a 0.5%–1% reactor may be selected after analyzing and calculating switching overvoltage of the capacitor bank, steady-state overvoltage during normal operation, and capacitor-terminal voltage rise caused by reactive-power overcompensation.
Based on the above selection principles, the following recommendations apply to series reactors in reactive-power compensation equipment:
(1) Selection of series reactors for capacitor installations in new substations must be handled carefully. Reactors and capacitors must not be combined arbitrarily; the harmonic background at the capacitor connection point must be considered.
(2) For capacitor installations already in operation, the rationality of the selected series reactor should be further verified and on-site measurements should be organized to understand changes in the grid harmonic background. For capacitor installations with a properly selected reactance rate, capacitor-bank capacity should not be increased or decreased arbitrarily.
(3) When capacitor-bank capacity varies significantly, a reactor with tap settings that can be adjusted synchronously with the capacitor may be used, or mixed reactor arrangements may be selected. By analyzing normal-operation steady-state overvoltage and capacitor-terminal voltage rise under reactive overcompensation, a 0.5%–1% series reactor may be selected to prevent overvoltage during capacitor-bank switching.
III. Basic Parameters of an Automatically Regulated Arc-Suppression Coil Complete System
1. Voltage level: 6 kV, 10 kV, 35 kV, 66 kV
2. Compensation current: Ic
3. Compensation-current range
4. Calculated capacity: P = U × I
5. Grounding transformer: whether provided. Generally, systems at 35 kV and above do not use a grounding transformer.
6. Grounding-transformer capacity: P = U × I + P2
7. Whether the grounding transformer has a secondary winding: P2
8. Insulation type of arc-suppression coil and grounding transformer: dry type/oil immersed
9. Installation location: indoor/outdoor
10. Indoor type: is an enclosure required? Dimensions!
11. Outdoor type: is a prefabricated substation enclosure or fence required? If yes, specify dimensions.
12. Is an isolating switch required in the connection of the complete equipment set?
Isolating switch: ① 6 kV and 10 kV model: GN19-12/400 (with manual operating mechanism)
② 35 kV model: GN19-40.5/630, with manual operating mechanism
13. Other standard accessories:
1) Surge arrester: ① 6 kV and 10 kV models: HY5WZ2-5/13.5 and HY5WZ-10/27
② 35 kV model: HY5WZ-30/80
2) Current transformer: ① 6 kV and 10 kV models: LZZB7-6-75/5 and LZZB7-10-75/5
② 35 kV model: LZZB7-35-75/5
3) Voltage transformer: ① 6 kV and 10 kV models: JDZJ-6/√3/0.1 kV or JDZJ-10/√3/0.1 kV
② 35 kV model: JDZX-35/√3/0.1 kV
