SPECIAL VOLTAGE STABILIZERS

The acronym BTS stands for Base Transceiver Station and is used to indicate all the transmitting and receiving devices that enable the radio coverage in a telecom cell.

This is definitely an application where high quality voltage supply, regardless of the incoming fluctuation, is very often the key for ensuring efficiency and reliability, fundamental qualities to guarantee operating continuity.

Disrupted service, loss of data, security failure, inaccurate information and general inconvenience are examples of possible problems caused by unstable supply. Of course, all this results in increased costs. A voltage stabilizer is a device able to respond to changes in the voltage level on the input line caused by sags (due to undersized distribution lines, connection of large loads to the network, ground faults, etc.) and surges (generated by disconnection of large loads, increased voltage at the generating plant, atmospheric events, etc.) The duration of such phenomena depends on their cause and is not easily predictable. Sags are generally more common especially where the distribution is not efficient.

The voltage stabilizer specifically designed for BTS sites has proved to be an efficient solution in the telecommunication field.

In comparison to a standard voltage stabilizer, a BTS unit offers the following characteristics:

• IP54 metallic enclosure for outdoor installation.
• Manual by-pass.
• Input and output circuit breakers.
• Input digital voltmeter.
• Output Class II surge arrestors.
• Optional isolating transformer.

The stabilizers can be single-phase, three-phase or specifically designed for receiving a three-phase input and releasing a single-phase output. With the three-phase configuration, the regulation is performed independent on each phase and the voltage stabilizer requires the neutral wire presence for a correct operation. If the neutral wire is not available, the addition of a D/Y isolating transformer or neutral-point reactor is required.

Three-phase stabilizers can be used with three-phase loads and up to 100% unbalanced single-phase loads, even in case of asymmetric mains.

The instrumentation is installed on the cabinet door. An output digital multimetre provides with information on the line downstream the voltage stabilizer (phase and linked voltages, current, power factor, active power, apparent power, reactive power, etc).

Minimum voltage, maximum voltage, internal overheating and overload on the voltage regulator are signalled by an acoustic alarm.

The stabilizer exploits a microprocessor-based control logic.

Main features

• Power design based on the maximum input current.
• Regulation based on the «rms voltage» and insensitivity to harmonics on the mains.
• Full functionality with load charge variable from 0 to 100%.
• Up to 30% harmonic content admitted on the load current.
• Insensitivity to the load power factor.
• No generation of noticeable harmonics in the output voltage.

Protections and signals

• Motor rotation stop due to regulation reaching the limit switches.
• Maximum and minimum line voltage alarm.
• Ambient thermostat (set to 65°C).
• Automatic circuit breaker to protect the voltage regulator.
• Fuses to protect the auxiliary circuits.
• Class II surge arrestors.

ORTEA product range is completed by a range of line conditioners based on voltage stabilisers and provided with additional protective devices.

The following sketch shows the typical line conditioners:

• Input automatic circuit breaker (protection against short-circuit).
• Delta/Star or Delta/Zig-zag input isolation transformer (complete galvanic isolation between the mains and the load and cancellation of third and triplen harmonics).
• Class 1 SPD surge protective device (protection against lightning).
• Class 2 SPD surge protective device (protection against transients).
• EMI/RFI filter (protection against electro-magnetic and radio-frequency noise).

The acronym DVB stands for Digital Video Broadcasting and is used to indicate all the devices transmitting and receiving digital signal. The availability of high quality voltage supply is the key for ensuring operating continuity.

The BC series is specifically designed for DVB stations and consists of a digital voltage stabilizer able to compensate for voltage variation on the input line generated by sags or surges, completed by additional devices for the protection against transients and electric noise generated by electronic appliances.

Usually, a BC stabilizer includes

• Digital voltage stabilizer.
• Isolating transformer.
• Input & output automatic circuit breakers.
• Input Class I surge arrestors.
• Output Class II surge arrestors.
• EMI/RFI filter.
• Instrumentation (voltmeter/multimetre).

For outdoor installation, the unit is housed in side an IP54 metallic enclosure.

Small ratings can be assembled in enclosures suitable for installation in 19” rack cabinets.

AOTs (wave absorbers) are obtained by assembling in a cabinet a combination of protective devices to deal with transients carried by the distributing lines.

In order to achieve the most complete protection level, the AOT combines two complementary concepts: smoothing and filtering.

The task is performed through surge arrestors, isolating transformers, detuning reactors and capacitors.

AOTs must be installed upstream and in series to the equipment that needs protection in order to avoid inductive and /or capacitive effects on the lines.

Usually, AOTs include:

• Input automatic circuit breaker.
• Parallel surge arrestors (redundant system).
• Isolating transformer.
• Capacitors.
• Detuning/blocking reactor
• Output automatic circuit breaker.

The operation can be divided in three phases:

1. The surge arrestors discharge to ground the direct overvoltage energy.
2. The isolating transformer ensures galvanic isolation between the mains and the equipment to be protected.
3. The filtering module eliminates the residual energy.