Ring Main Unit

Normal operating conditions Design to relevant standard, with the following limit values:
a)Air temperature: ±40℃; Daily average ≤25°C
b)Altitude above sea level: Maximum installation altitude: 4000m

c)Wind: less than 35m/s;
d)Earthquake intensity: no more than 8 degrees;

3.1Main new advantages of RMR

The SF6 is contained in a welded stainless steel tank, which is sealed for life.The pressure system is defined as a sealed for life system with an operating life time exceeding 30 years. The leakage rate is less than 0.1% per year. In order to ensure a reliable and tight welding, all welding work is carried out by computer controlled robots. Electrical and mechanical bushings penetrating the tank are clamped and sealed to the tank by high quality O-rings. The mechanical bushing has in addition a rotating shaft which connects the shaft of the switch to the corresponding shaft of the mechanism. The rotating shaft is sealed by a double set of gas seals. All SF6-tanks have to pass a leakage test before gas fill-ing. Leakage test and gas filling are done inside a vacuum chamber. The first step in the leakage test is to evacuate all air inside both SF6-tank and vacuum chamber simultaneously. Then the SF6-tank is filled with Helium. Due to the characteristics of Helium this test will detect all possible leakages. If the SF6-tank passes this test, the Helium will be evacuated and replaced by SF6. The SF6-tank has a degree of protection of IP65 and can be immersed into water and still maintainable functions in a satisfactory way.

Wide selection of reliable quality switching products like load break switch, vaccum circuit breaker.

4.1 Load break switch

The load break switch is a 3-position switch disconnector and earthing switch using SF6 gas as an arc quenching meduim, the switch positioning is close-open-earthed. In the open position the switch satisfies the disconnector requirements

3-position load break switch (closed,open,ａnd earthed) Spring mechanism consists of single spring action, double spring operating mechanism. Among them, the double spring operating mechanism used in switchgear unit, can realize the automatic tripping trip.

4.2 Vacuum circuit beaker

RMR Vacuum circuit breaker has vacuum bottles as interrupters of the current. In series with the circuit-breaker main circuit is connected a 3-position disconnector/earthing switch. The operation between vacuum circuit breaker and disconnector/earthing switch is mechanically interlocked. Compact, simple structures and safe operation.

4.3 Fuse

By means of tripping device it operates as a switch-fuse combination. Two earthing switches are equipped in both sides of the fuse-links in order to ensure the personal safety of operators.

Both earthing switches are operated in one operation. The switch-fuse and earthing switch is mechanically interlocked to prevent unauthorized access to the fuse-links. The lower cover which gives access to the fuse-link is also mechanically interlocked with the earthing switch. The fuse holder is sealed tightly, so it is anti electirc dust ａnd moisture.

Note: Fuse selection for transformer protection selection refer to IEC fuse standard.

5.1Gas pressure/density meter

Density meter with Low voltage pressure alarm	General density meter

Each tank of RMU is equipped with density meter to monitor the gas pressure inside. The pointer of the meter is in the green area, that means the normal pressure in the gas tank, if the pointer is in the red zone, it means the pressure of the tank is low. It is required to periodically inspect the density meter, to ensure the pressure in the normal range. Additionally, density meters with low pressure alarm is also available as an option. The meter is provided as the customer specified.

Type C Bushing

Type C Bushing	The connection of the HV-cables is made by cable Type C bushings. See right side pictute. The Type C bushings are made of cast resin epoxy with moulded-in conductors.This C type is used together with full-screened elbow cable connectors which is an ideal solution for areas with humidity or condensation problems is achieved
Voltage indicator	Each unit is equipped with voltage indicator with phase check outlet,which feature:Stable performance,High brightness, Wide viewing angle,long life.
Fault indicator	Fault indicator is provided as an option Fault indicator for detection of a short circuit, single phase earth fault. Accurate detection and clear indication.

Above components of RMU is standard equipped, any special requirement pls consult us.

CT/Zero sequence CT

CT/Zero sequence CT are provided according to the customer’s requirement. a.Installed on external bushings when need.CT should be earthed reliable,ａnd open circuit of secondary side is not allowed,or it will lead to severe damage to the equipment and even dangers to the individuals.

Elbow cable connector and relevant accessories

-Frontal Elbow Cable connectors -Copper conductors -Press cores -Copper lugs -Additional back cable connector optional -Additional elbow connector type surge arrester

Operating Handle

The operating handle has two sides,for both Load break switch,circuitBreaker,ａnd earthing switch manual operation,

Protection relay

RP260 protection device is numerical protection relay with self-powered. -OC/EF protection -Fault report -UV/OV protection -Frequency protection -Other required is discussable

Note:
Above is dimension for three unit combination, all the dimension about CCC, FFF,CCV, VVV,CVV, CFV, FFV, CCF is same.

Extension way by top connection

For normal Ring main unit combined by three unit together, above picture reference is shown us.If special required more, pls consult us.

Technical service

Rockwill,China. Provide with best support,

If you have any question pls consult below.

Rockwill, CHINA. Tel: 0086-

Rockwill, CHINA. : barry@rockwill.cn