Case 1 - Substation for electrical utility company

This is for an electric utility company’s substation on a remote island. The low potential of the system raised concerns about voltage drops due to the inrush current of the power receiving transformer. The Inrush Limiter T1 was installed to prevent this.

Figure 3-2 shows measured waveforms, recorded during field validation testing, of the inrush current and voltage drop with and without the Inrush Limiter.

Transformer specifications Tr.1: 10MVA 22kV/6kV
Tr.2: 6MVA 22kV/6kV

After repeated opening and closing tests without the Inrush Limiter, the inrush phenomenon showed an inrush current of 411 A, and voltage drop of 14.8%. With the Inrush Limiter, the inrush current was suppressed to 91A and the voltage drop was held to within 1.9%.

Figure 3-1
Figure 3-2

Case 2 - Electrical Power Receiving Substation at a Major Chemical Manufacturer

A major chemical manufacturer owns an electrical furnace and their own electrical power receiving substation. The substation consists of several banks of power receiving transformers. When they energized a transformer in one of the banks, the other banks (connected to the primary side of the power system) showed a significant voltage drop. The Inrush Limiter T1 was installed to avoid this voltage drop and the disturbances it causes on manufacturing activities.

Figure 3-4 shows measured waveforms, recorded during field validation testing, of the inrush current and voltage drop with and without the Inrush Limiter.

Transformer specifications 22MVA 44kV/11kV

After repeated opening and closing tests without the Inrush Limiter, the inrush phenomenon showed an inrush current of 1,514A, and voltage drop of 7.1%. With the Inrush Limiter, the inrush current was suppressed to 83A and the voltage drop was held to within 0.2%.

This manufacturer used a circuit breaker with a resistor for many years to suppress inrush currents in their 66-kV electrical power receiving substation. (The 66-kV serial resistor is used with an auxiliary circuit breaker to limit inrush current when the breaker is closed.) The Inrush Limiter has rendered these resistors obsolete, which are now removed.

Figure 3-3
Figure 3-4

Case 3 - Substation for Wind Power Generators

Studies at an interconnected substation for a wind power generating system revealed voltage drops of 20% when the transformer was connected. It was necessary to suppress this to within 5%. The Inrush Limiter achieved less than 3%.

(Each of the following countermeasures to achieve 5% or less were rendered obsolete:

  1. Installation of a diesel generator
  2. special designed transformer (change in leakage impedance, etc.)
  3. Use of a serially-connected resistor and circuit breaker

Figure 3-6 shows measured waveforms, recorded during field validation testing, of the inrush current and voltage drop with and without the Inrush Limiter.

Transformer specifications 30MVA 33kV/66kV

After repeated opening and closing tests without the Inrush Limiter, the inrush phenomenon showed an inrush current of 839A, and voltage drop of 19.5%. With the Inrush Limiter, the inrush current was suppressed to 164A and the voltage drop was held to within 1.5%.

Figure 3-5
Figure 3-6

Installed Base

Customer Application Transformer Specifications Units
Voltage [kV] Windings
Capacity [MVA]
Asahi Kasei Co., Ltd., Nobeoka Plant Chemical factory:
Heavy electrical power user. Used for a own extra high-voltage substation.
60/12 Y-Δ 1
33
Kyushu Electric Power Company, General Research Laboratory Applied as a portable 1
Kyushu Electric Power Company, Azetsu Substation Utility substation for island:
6.6 kV to 66 kV receiving substation
Station 1,2&4 6.6 / 66 Y-Δ 3
25
Utility substation for island:
6.6 kV to 66 kV receiving substation
Station 3 66 / 22 Y-Y 1
20
Asahi Kasei Co., Ltd., Nobeoka Plant Chemical factory:
Heavy electrical power user. Used for a own extra high-voltage substation.
66/11 Y-Δ 1
17.1
Asahi Kasei Co., Ltd., Nobeoka Plant Chemical factory:
Heavy electrical power user. Used for a own extra high-voltage substation.
60/11 Y-Δ 1
30 / 40
Kyudenko Corporation Wind power generating station:
Electrical power transmission
66 / 22 Y-Δ 1
14
Nishinippon Plant Engineering and Construction Co., Ltd. Wind power generating station:
Electrical power transmission
66 / 22 Y-Δ 1
20
Kyudenko Corporation Wind power generating station:
Electrical power transmission
66 / 22 Y-Δ 1
20
Asahi Glass Co., Ltd., Chiba Plant Glass manufacturing factory:
Heavy electrical power user, using an electric furnace for glass manufacturing
11 / 0.534 Δ-Y-Δ 4
14.38×2
Showa Denko KK, Omachi Plant Electric furnace for manufacturing factory:
Heavy electrical power user, using electric furnace for carbon graphite electrodes manufacturing.
44 / 14 Δ-Δ 3
41.5
J-POWER, Electric Power Development Co., Ltd. Wind power generating station:
Electrical power transmission
66 / 33 Y-Δ 1
29.5
Railway Technical Research Institute R&D Center:
Research and development for power transmission into railway technologies and labor science.
for R&D 1
Oji Paper Co., Ltd., Nichinan Factory (shipped via Meidensha Corp.) Paper manufacturing factory:
Switching electrical power source between own powerhouse and power company
66 / 11 Y-Y-Δ 1
32/32/15
Nisshin biomass power station Electric power selling:
Switching electrical power transmission between own biomass power station and power company.
22 / 6.6 Δ-Δ 1
7
Kyushu Electric Power Company, Inc., Urakuwa Substation Utility substation for island:
6.6 kV to 22 kV receiving substation
6.6 / 22 Y-Y 1
15
Kyushu Electric Power Company, Inc., Ojika Substation Utility substation for island:
22 kV to 6.6 kV receiving substation
Station 1 22 / 6.6 Y-Y 1
10
Station 2 22 / 6.6 Y-Y 1
6
JNC Corporation, The First Substation Chemical company:
Switching electrical power source between own powerhouse and power company.
Station 1 66 / 18.4 Y-Δ 1
25
Station 2 66 / 18.4 Y-Δ 1
8
Station 3,4 18.4 / 3.3 Δ-Δ 1
12.5
JNC Corporation, Tsuru Power Plant Hydroelectric generating station:
Electrical power transmission.
63 / 6.6 Y-Δ 1
12
Showa Denko KK, Omachi Factory Electric furnace for manufacturing factory:
Heavy electrical power user, using electric furnace for carbon graphite electrodes manufacturing.
44/11 Δ-Y 1
22
39 / 0.57 Δ-Y 1
22
KYOCERA Communication Systems Co., Ltd Photovoltaic power generating station :
Electrical power transmission.
66 / 22 Δ-Y 1
30
Denka Company Limited Oomuta factory Electric furnace for manufacturing factory:
Heavy electrical power user, using electric furnace.
66 / 0.18 Y-Δ⇔
Δ-Δ
1
9×3
Shimonoseki City
[FUJI ELECTRIC CO., LTD. Kansai branch office]
Incineration system 22 / 6.6 Δ-Δ 1
3.5
Daido Steel Co., Ltd. Shibukawa factory Electric furnace for manufacturing factory:
Heavy electrical power user, using electric furnace.
38 / 0.57 Δ-Δ-Y 1
2.8×2
J-POWER Electric Power Development Co., Ltd. Wind power generating station :
Electrical power transmission.
72 / 22 Y-Δ 1
23
Shimonoseki City
[FUJI ELECTRIC CO., LTD. Kansai branch office]
Incineration system 22 / 6.6 Δ-Δ 1
3
Meiden Plant Systems Corporation Photovoltaic power generating station :
Electrical power transmission.
66 / 22 Y-Δ 1
21
Suzuka Electric Works Co., Ltd. Photovoltaic power generating station :
Electrical power transmission.
22 / 6.6 Δ-Δ 1
10
Showa Denko KK, Omachi Factory Electric furnace for manufacturing factory:
Heavy electrical power user, using electric furnace for carbon graphite electrodes manufacturing.
44 / 42~29 Y-Y 1
32.3
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