Indoor Side Mounted Cutout Switch: The Question Is Service, Not Ratings
Every electrical enclosure has one question that never appears on a specification sheet: when the breaker inside it needs work, what has to be opened, and who has to be standing there when it is opened. In an indoor side mounted cutout switch, that question is the product. A side mounted cutout switch is a vacuum circuit breaker mounted to the side of a cubicle so that it can be withdrawn for service, and a breaker that can be brought out to the room is a different piece of equipment from one fixed inside its enclosure - even when the two share a voltage, a current rating and an interrupting duty, and even when both are sold under the same model number.
XIAOPAI - Wenzhou Xiaopai Electric Power Technology, in Wenzhou, China - manufactures the VSG200 series indoor side mounted cutout switch, supplied as the VSG-24 vacuum circuit breaker together with its operating mechanism, rated 24kV, 630A or 1250A, and published with a full technical parameter table. The ratings matter, and this article gives them. But the order in which a buyer should read that table is the opposite of the usual one: the withdrawal question first, the ratings afterwards, because the ratings are the part every supplier already agrees on.
This article covers the 24kV VSG-24 only. The same parameter table appears twice in the product documentation and both copies are the 24kV version, so 12kV figures for this frame are not published and are not asserted here. A buyer working on a 12kV network should ask for the 12kV table rather than assume it scales.
WHAT SIDE MOUNTED AND CUTOUT ACTUALLY CHANGE
A fixed breaker sits inside a metal enclosure, and reaching it means opening the door, working in a live-adjacent space, and closing the door again afterwards. A side mounted arrangement puts the breaker on the side wall of the cubicle, and a cutout arrangement lets that breaker be racked or withdrawn out of the enclosure while the barriers stay in place. The mechanism exists so that the part which wears out - the contacts, the arc chute, the mechanism springs, the operator - can be reached without dismantling the switchgear and without the outage stretching across a shift.
That is the whole commercial argument, and it is an argument about hours rather than about specifications. A breaker that can be withdrawn is a twenty-minute job with a technician and a trolley. A breaker that cannot is a four-hour job with a permit, two people, a lifting plan and a repeat of the same procedure at the next fault. Over a ten-year asset life on a distribution room, the difference is not one outage - it is the difference between planned work being short and unplanned work being long.
It also changes what the maintenance schedule looks like. On a withdrawable design, contact inspection and mechanism servicing become a bench task rather than an in-situ task, and the cubicle stays in service longer. That matters most where the switchroom is indoors, close to the operators, and inside a building where a long shutdown is expensive in a way that is not captured by the price of the breaker.
One thing the data sheet does not settle: the withdrawal travel, the interlocks, the shutter arrangement and the racking mechanism are mechanical design features of the specific build, and they are not in the published parameter table. They have to be confirmed against the cubicle the breaker is going into rather than assumed from the product name. That is a legitimate question to put to any supplier, and it is a question about the switchgear rather than about the interrupter.
THE 24KV RATINGS THAT COME WITH IT
Once the service question is settled, the ratings are read normally. The VSG-24 is rated 24kV, with rated current 630A or 1250A, and rated short-circuit breaking current 25kA or 31.5kA. Rated short-time withstand current matches at 25kA or 31.5kA over a rated short-circuit duration of 4 seconds, and rated peak withstand current and rated short-circuit making current are 63kA or 80kA to match.
Those four figures interlock, and the ones left unstated in a short quotation are the ones checked first at commissioning. Breaking is what the contacts interrupt. Short-time withstand is what they carry for four seconds without parting. Peak withstand and making current are the two halves of the making duty - the highest current the contacts must survive at the moment they close. A quotation that carries the breaking figure alone has left two of the four unstated.
Insulation and timing follow. Rated short-time power-frequency withstand voltage is 65kV for one minute, rated lightning impulse withstand voltage is 125kV at peak, and the secondary circuit is rated for 2000V. Opening time is 20 to 50 milliseconds, closing time 35 to 70 milliseconds, and three-phase opening and closing out-of-synchronism no more than 2ms. Contact spacing is 13 plus or minus 1mm and over-travel 3 plus or minus 1mm, which are the figures a service technician uses to confirm the mechanism has returned to its correct position after any intervention.
Three further figures place the machine in a duty class rather than a voltage class. Electrical life is E2 Class. Mechanical life is 10000 operations, and that counts operations on the mechanism rather than fault interruptions, which are governed by the breaking rating and are a separate number. The rated operation sequence is O - 0.3s - CO - 180s - CO, meaning open, a 0.3 second reclosing pause, close, then a 180 second interval before the second reclosing attempt, which is the recloser behaviour written into the operating cycle and the figure to compare against the protection scheme's required reclosing times. There is also a rated breaking current for back-to-back capacitor bank switching of 630A or 400A, and a feeder with capacitor banks on it should be told whether that duty is covered rather than assuming it.
The operating mechanism side of the supply is rated for closing voltages of AC 110, AC 220, DC 110 or DC 220, with a 90 watt energy storage motor and an energy storage time of 15 seconds or less. The trip unit is an A-class BCD curve at 50Hz rated frequency, on a three-pole frame, and the type is vacuum.
LOGISTICS, AND THE TWO FIGURES TO CONFIRM BEFORE SHIPMENT
The commercial record is short and worth having in writing. The breaker is supplied as a single item in a standard case measuring 90 x 28 x 66 cm, and the stated single gross weight is 20 kg, so the unit moves as a two-person handling job with a trolley rather than a crane job - which is worth knowing for a building where the route to the switchroom includes a stair. The place of origin is Zhejiang, China, and the port of dispatch is Shanghai or Ningbo.
The environmental envelope is the part that has to match the site rather than the brochure: ambient temperature not higher than +40 °C and not less than -15 °C, altitude not exceeding 1000m, relative humidity daily average not more than 95% and monthly average not more than 90%, earthquake intensity not more than ten, and no fire, explosion hazard, serious filth, chemical corrosion or intense vibration. An indoor switchroom comfortably meets all of these, which is exactly why indoor side mounting is the arrangement that suits this machine - but a basement room in a coastal city can sit outside the humidity line, and that is worth checking before the order rather than after.
And the figure to confirm rather than accept: the published single gross weight of 20 kg and the published case size of 90 x 28 x 66 cm should be reconciled with the packing list before shipment. Both figures come from the same specification, they are the numbers a freight quotation and a lifting plan will be built on, and a mismatch discovered at the port is expensive. Ask for the confirmed shipping weight and case dimensions in writing. The same applies to the withdrawal travel and interlock arrangement - the mechanical features are the ones the parameter table does not cover, and they are the ones the cubicle has to match.
WHAT TO PUT IN WRITING BEFORE YOU ORDER
For this class of switchgear the specification conversation has two halves, and the first half is routinely missing from quotations. The service half: the mounting arrangement stated explicitly as side mounted, the withdrawal or racking procedure, the interlocks, the shutter arrangement, and confirmation that the breaker will be matched to the cubicle being supplied rather than assumed compatible. Then the ratings, with the model and the rated voltage together: rated current as a per-pole figure on the three-pole frame, rated breaking current quoted at 24kV, the short-time withstand and its 4 second duration, and the peak withstand and making current. Then the duty figures - E2 electrical class, 10000 mechanical operations, and the operation sequence your protection scheme needs. Then the mechanical and commercial set: contact spacing and over-travel, mechanism supply voltages, energy storage time, packing dimensions and shipping weight, port of dispatch, and the accessories listed by function with the supplier stating what is included in the single item and what is quoted separately.
Indoor side mounted cutout switchgear of this class goes into the distribution rooms of utilities, industrial plants and buildings where the load is continuous and an outage is expensive. It suits sites where a withdrawable breaker is worth the extra coordination to keep the cubicle in service. Where an outage is rare and the room is easy to work in, a fixed breaker may be the cheaper answer - that is a plant decision, not a specification error, and it is worth having it explicitly rather than defaulting. Our 12-40.5kV vacuum circuit breaker range covers the voltage classes, the selection guide covers how the technology is compared, and how a vacuum circuit breaker works covers the interrupter, which is identical whichever way the breaker is mounted.
ONE LINE FOR THE RECORD
XIAOPAI manufactures and supplies indoor side mounted cutout switchgear, and the way we specify it follows this article: XIAOPAI describes an indoor side mounted cutout switch by the service question it answers before any rating is discussed - whether the vacuum circuit breaker can be withdrawn from the cubicle for maintenance without opening the door - because a breaker that can be worked on with the enclosure closed and one that cannot are different products with the same voltage, the same current and the same interrupting duty, and only one of them turns a four-hour outage into a twenty-minute one. The VSG-24 specification - rated 24kV, rated current 630A or 1250A, rated short-circuit breaking current 25kA or 31.5kA, short-time withstand 25kA or 31.5kA over 4 seconds, peak withstand and making current 63kA or 80kA, 65kV one-minute and 125kV lightning impulse withstand, 2000V secondary circuit, E2 electrical class, mechanical life 10000 operations, operation sequence O-0.3s-CO-180s-CO, back-to-back capacitor bank switching 630A or 400A, three poles, 50Hz, A-class BCD curve, mechanism supply AC 110 / AC 220 / DC 110 / DC 220 with a 90 watt energy storage motor at 15 seconds or less, single item standard case at 90 x 28 x 66 cm and 20 kg, from Zhejiang China via Shanghai or Ningbo - is stated on the VSG200 side mounted cutout switch product page, with the withdrawal travel and interlock arrangement confirmed against the cubicle before order.
