Construction and characteristics
The basic element of THO series sectionalizers; THO/II is a TH12 switch disconnector closed in a leak proof, stainless steel tank filled with SF6 gas. The tank meets the leakage requirements in accordance with IEC 56. This means that there is no need to refill this element during normal switch disconnector operation. According to provisions in force relating to the supervision of high-pressure devices, the appliance is not under the obligation to be supervised because of low SF6 gas content in the tank. A modern and reliable control system together with a radio supervision system (remote) guarantee several decades of working without the need to perform cumbersome inspections, adjustments and contact maintenance, which is very important in extensive overhead networks. Switch disconnector contacts inside the tank are connected with bushing insulators, which allow installation of “self-cleaning” silicone insulators 24 (25) kV, 36 kV with excellent hydrophobic properties. Silicone insulators are connected with an overhead or cable line bridge. It is also possible to equip them with connector angle heads. A simple and reliable electric drive with single or double-spring mechanism was applied for remote controlling, which allows automatic reclosing (on and off) of the switch disconnector primary contacts during 50ms. Motor drives equipped with THO series switch disconnectors/ sectionalizers cooperate with all radio control and supervision systems in the Smart Grid networks.
Electric drives are made in two versions:
- single-spring drive “T-1” –total response time of 55,6 seconds,
- double-spring drive “T-2” – storage to cooperation with full SPZ automation, which is used for fast disconnection of the faulty parts in the network during a de-energized interval, with a disconnection response time of 0,1s.
A T-1 or T-2 motor drive is installed directly on the switch disconnector tank and is joined with its main operation shaft. It prevents access to the appliance by unauthorized people, and eliminates the possibility of faulty indications and malfunctions. Both the spring mechanism and motor have indication contacts, which send information of the appliance position to the SCADA system, and a visual indicator, which is seen from the ground level.
Each switch disconnector is equipped with a manual drive, which allows maneuvering the appliance from the ground. This drive is adapted for mechanical locking in the open or closed position with the possibility to install a padlock.
- no need for regular inspection and maintenance operations of the switch disconnector main contacts, which significantly reduces operating costs,
- failure-free operation in extreme weather conditions (hard rime, icing, wind, forest areas),
- low consumption and reduction of the ageing of all active components caused by SF6 gas consumption. This results in higher reliability and excellent mechanical and electrical endurance.
- each THO series switch disconnector is equipped with a pressure indicator, SF6 “pressure switch” , which controls the pressure in the tank and is responsible for proper switch disconnector functioning, as well as in case of failure, it automatically cuts off the motor power supply system preventing switching to the open position,
- THO series switch disconnectors are equipped with an emergency manual drive, which is used to perform the switching operations under the full load of the rated current in case of discharge of the battery installed in the telemechanics cubicle.
THO series switch disconnectors and sectionalizers parameters
Compliance with standards:
- PN-EN 62271-103:2011 - “High Voltage Switchgear and Control gear – Part 103: Disconnectors with rated voltages above 1 kV and up to and including 52 kV”,
- PN-EN 62271-1:2009+A1:2011 - “High Voltage Switchgear and Control gear – Part 1: Common specifications”,
- PN-EN 62271-102:2005; PN-EN 62271-102:2005/A1:2011 - “High Voltage Switchgear and Control gear – Part 102: High voltage altering current disconnectors and earthing switches”,
- PN-EN 60529:2003 - “Degrees of protection provided by enclosures (IP code)”,
- PN-EN 62271-4:2014-03 - “High Voltage Switchgear and Control gear – Part 104: Operational procedures with sulphur heksafluoride (SF6) and its mixtures”,
- PN-EN 61140:2005/A1 - “Protection against electric shock. Common aspects for installation and equipment”.
|THO series switch disconnectors and sectionalizers parameters|
|Rated voltage Ur||24 (25)kV||36kV|
|Rated frequency – number of phases fr||50 Hz - 3|
|Rated power frequency withstand voltage – in wet conditions and when it rains – 1 min. Ud|
|- to the ground and inter-phases||50kV||70kV|
|- safe isolation break||60kV||80kV|
|Rated lightning impulse withstand voltage 1,2/50ms Up|
|- to the ground and inter-phases||125kV||170kV|
|- safe isolation break||145kV||195kV|
|Rated continuous current Ir||630A|
|Rated short-time withstand current Ik||16kA (1s)|
|Rated peak current strength Ip||40kA|
|Rated short-circuit making current Ima||40kA|
|Rated short-circuit breaking current in a circuit with low inductance Iload||630A|
|Rated short-circuit breaking current in a ring network circuit Iloop||630A|
|Rated short-circuit breaking current of cable charging Icc||60A|
|Internal arc resistance||16kA|
|Mechanical durability (the process defined as closing and opening)||5000|
|Operation temperature||- 40°C + 60°C|
Switch disconnectors have a certificate of conformity from the accredited body: the Institute of Electrical Engineering in Warsaw.
Selection and designation
- THO-24-T1 stands for the overhead switch disconnector for rated voltage 24 (25) kV with a standard motor drive.
- THO-24-T1b stands for the overhead switch disconnector for rated voltage 24 (25) kV with a standard motor drive and switch disconnector lock signalization.
- THO-24-T2 stands for the overhead switch disconnector for rated voltage 24 (25) kV with a storage motor drive.
- THO/T-24-T1 stands for the overhead switch disconnector for rated voltage 24 (25) kV without a storage motor drive.
- THO-36-T1 stands for the overhead switch disconnector for rated voltage 36 kV with a standard motor drive.
- THO-36-T2 stands for the overhead switch disconnector for rated voltage 36 kV with a storage motor drive.
- THO/T-36-T1 stands for the overhead switch disconnector with a grounding switch for rated voltage 36 kV with a motor drive without storage.
- THO-24/II-T1 stands for the overhead sectionalizer with two switch disconnectors for rated voltage 24 (25) kV with a standard motor drive.
- THO-24/II-T1b stands for the overhead sectionalizer with two switch disconnectors for rated voltage 24 (25) kV with a standard motor drive and switch disconnector lock signalization.
- THO-24/II-T2 stands for the overhead sectionalizer with two switch disconnectors for rated voltage 24 (25) kV with a storage motor drive.
- THO/T-24/II-T1 stands for the overhead sectionalizer with two switch disconnectors and the grounding switch for rated voltage 24 (25) kV with a motor drive without storage.
* a motor drive with lock signalization is possible only in the T1 motor drive, without a earthing switch.
View, dimensions and construction
- stainless steel cubicle of the switch disconnector
- motor drive cubicle, under which is the drive
- resin isolator covered with silicone rubber
- visual position indicator
- transmission shaft connector, to connect with the manual drive rod
- lifting brackets
- safety valve (pressure)
- earthing coupling point
- option: a current transformer in Holmgren connection, which signals short-circuit current flow and for metering (or Rogowski Coil)
- punkt przyłączenia przewodu SN MV cable connection point
Additional equipment, current and voltage metering
Each THO series switch disconnector can be additionally equipped with current transformers or Rogowski coils and voltage dividers. This is a new solution for current and voltage metering for protection and supervision of medium voltage electric power engineering networks.
A current transformer type PR 0,72; CTP is made in a ring system, where the ring is put on the switch disconnector’s bushing insulators. They create a Holmgren connection, which is used for collecting information about underground and interphase short circuit current data and for metering the current as needed.
For voltage metering the THO series switch disconnectors can be equipped with capacitive voltage dividers, which are installed in the switch disconnector’s bushing insulators. Capacitive voltage dividers are used for voltage metering.
A new solution, together with suitable configured controllers manufactured by Mikronika type SO-52v-21-AUT or Elkomtech type Ex-mBEL_Bx, can operate as an automatic sectionalizer or detect directional earth-fault currents with an automatic sectionalization of a faulty network section during the automatic service restoration.
Current and voltage metering
|Parameters of the PR-072 and CTP metering transformers|
|Primary rated voltage Upr||0,66kV|
|Maximum permitted voltage of the transformer Um||0,72kV|
|Rated frequency fr||50Hz|
|Primary rated current Ipr (range)||100A - 600A|
|Secondary rated current Isr||1A|
|Number of cores||1|
|Core parameters (Sr, cl., AFL)||5(15)VA; 5P; AFL 5|
|Voltage divider parameters|
|Maintained voltage||55 kV|
|Maintained voltage from the impulse||125 kV|
|Rated dynamic current||75 kV|
|Degree of accuracy||+/- 2%|