Products of ACER VOLTAGE company protects of its customers‘ equipment from the devastating effects of the surge.
This company acted since 2006 under the name ACER HK Ltd. and in the end 2014 moved into a new place of work, where it remains. In 2016, the company renamed to its current name ACER VOLTAGE Ltd. that better reflects its focus and activities.
In the past, the company developed and manufactured varistors based on ZnO surge arresters in the LV applications and then another surge arresters made from them. The first type was a surge arrester SP 0.440 / 10, which has been improved and is now produced only in design SPB * / 10 in various voltage levels acc. to type of installation. Production of ZnO varistors was abolished in 2006, and for current and surge arresters are only used varistors from external suppliers. Another significant part of production program are polymeric arresters for HV networks of 1-39 kV for AC or DC networks . They consist of the entire model range, which is constantly expanding. In addition, it is possible to produce nonstandard types according to customer requirements and specifications. Details about today‘s sortiment ACER VOLTAGE can be found at our catalog or website. Recently was expanded assortment of products with gas-filled power arresters.
The Company has acquired and regularly renews certification according to DIN EN ISO 9001 certified.
ACER VOLTAGE is a leading company supplying technology for power and automation that enable energy and industry could increase its efficiency while reducing their impact on the environment. ACER VOLTAGE products are delivered to 42 countries and are always close to its customers. With superior technology, global scale, deep industry expertise and local knowledge, we can offer our customers products, system solutions and services that help improve the reliability of their transmission networks.
Due to focus and strengths in technologies for power and automation, we strive for organic growth. Our global manufacturing base ensures consistent products and systems of the highest quality produced in the ACER VOLTAGE for customers worldwide. Our customers have easy access to a full range of products, either directly with us as the manufacturer, or through a network of distributors or wholesalers, which is constantly expanding.To ensure the quality of products the company ACER VOLTAGE performs 100% inspection at production testing equipment. With these devices are controlled precise technical specifications throughout the production company ACER VOLTAGE.
Definition of overvoltage
Overvoltage is voltage that exceeds the maximum value of operating voltage in an electric circuit.
Pulse overvoltage, its formation and division
According to its origin, pulse overvoltage is classified into:
- atmospheric overvoltage (LEMP – Lighting ElektroMagnetic Pulse)
- switching overvoltage (SEMP – Switching ElektroMagnetic Pulse)
- overvoltage formed during discharges of static electricity (ESD – ElektroStatic Discharge)
- overvoltage due to nuclear explosions (NEMP–Nuclear ElektroMagnetic Pulse)
Atmospheric overvoltage (LEMP)
They are the most dangerous and is induced primarily by thunderstorms with lightning discharges. Overvoltage may occur between a phase and the earth, or between phase conductors. It is caused primarily by thunderstorm activity, specifically by lightning discharges. Overvoltage due to lightning manifests itself most on overhead lines and in sections of unshielded cables.
Atmospheric overvoltage may be generated by:
- a direct or near strike of lightning into a lightning conductor, metal structure, cable...
- the destructive effect of lightning current is given by high energy liberated in a short time, causing:
- a voltage drop on earth resistance
- induced voltage in loops
- a distant strike of lightning into overhead lines, causing surges of overvoltage following even after a cloud-cloud discharge or after a lightning strike near the line
- a distant lightning strike diverted to the grand causing a lightning-channel field
Switching overvoltage (SEMP)
They are very frequent overvoltage that occurs in both low-voltage and high-voltage networks.
Switching overvoltage is generated by industrial activities:
- when great loads, especially inductive ones, are switched on and off, e.g. transformers or electric motors or even small household appliances, e.g. refrigerators, freezers
- in the event of short circuits in a distribution network and the like.
ZnO Overvoltage Limiters
The parameters on the basis of which we design the limiters are as follows:
- Continuous operating voltage of the limiter UC – it represents the maximum value of voltage connected permanently to limiter terminals at mains frequency.
- Rated voltage of the limiter UR – it represents the maximum effective value of voltage for which the limiter is designed while the correct function under conditions of temporary overvoltage at mains frequency is maintained. Such voltage is defined as voltage to which the limiter is exposed for 10 seconds following previous stress.
- Protective level of the limiter UP – is voltage on terminals at a given shape and peak value of current passing though.
- Nominal discharge current IN – the peak value of an atmospheric current pulse that is used for the classification of overvoltage limiters.
- Residual voltage URES – it represents residual voltage on the overvoltage limiter. It is actually the peak value of voltage that appears between terminals of the overvoltage limiter when discharge current is passing through it.
- Working temperature ϑ – it represents the range of permissible ambient temperatures stated by the manufacturer for the limiter to work properly.
- Line discharge class – a number expressing the ability of the overvoltage limiter to absorb energy in the event that long lines are discharged.
Overvoltage resistance of ZnO limiters
The energy classes and an example of their use
- Class I. – use in HV networks without classification of class (5kA) or class 1 or 2 (10 kA)
- Class II. – use in 110 kV networks
- Class III. – use for 110-400 kV networks and for cable networks
- Class IV. – 400 kV long lines
- Class V. – extremely extensive 750 kV cable networks
Sizing of the overvoltage limiters
Selecting the operating voltage UC of limiters
Incorrect selection of voltage UC may have a negative effect on its function:
Characteristics of overvoltage protection of LV and HV networks
In LV and HV distribution networks with overhead lines, it is necessary to protect equipment primarily from atmospheric overvoltage. Switching overvoltage reaches substantially lower current and voltage levels than atmospheric.
The greatest overvoltage in cable networks without connected overhead lines is caused by short circuits and/or switching.
The primary task of protective measures which are economically fully justified is to protect the equipment of LV networks from destruction by atmospheric overvoltage by installing surge arresters and, at the same time, to enable the protection of installation by adequately reducing overvoltage in the network.
Principles for positioning and connecting in LV networks
Generally applicable rules for connecting HV limiters
Four rules, which can be applied generally to protection in VN networks, follow the above characteristics:
- The overvoltage limiters and the device that is to be protected must be earthed to a common earthing system. The galvanic interconnection between the earthing terminals of the limiters and the earthing of the protected device must be as short as possible.
- The total length of conductors a and b of connection of the limiters to the protected device must be as short as possible.
- It is always recommended that conductor b should be as short as possible or at least shorter than conductor a.
- Strip conductors are more suitable for connection than those with circular cross-section as with the same cross-section strip conductors have smaller inductance and pulse losses of overvoltage in them are smaller. The minimum size of a connecting conductor is 6 mm. The minimum width of a strip conductor is 12 mm.
Above all, the installation of overvoltage limiters is prevention of possible damage. A seemingly considerable cost of such protections tend to be only a fraction of a per cent of the acquisition value of the technology protected and a negligible sum for possible damage caused by breakdowns and destruction of technological equipment. Unprotected electric distribution systems, computer and data networks always pose a considerable risk to their users.
One-line diagram of protection with the marking of sections of conductor a and conductor b
Connection of the limiters to the transformer
Ground plan of the earthing network of limiters at the transformer
Connection of the limiter: (a) correct connection, (b) incorrect connection
Maintenance and inspection of overvoltage limiters
- After any changes in protective elements belonging to the system installation
- Periodically, at least 1 year
- After direct strike to the protected instalation