1.1 Summary

The following specification is intended for use by consultant engineering firms to provide bidding specifications for products with the quality and performance characteristics required for an Automatic Voltage Regulator. The Automatic Voltage Regulator; hereafter, will be refereed to as an “AVR” or “GSR”. The GSR is designed to maintain constant voltage and power line conditioning to the equipment load under a wide variety of conditions, even when the utility input voltage, frequency, or system load vary widely. The GSR shall consist of an all copper, multiple tapped, triple shielded isolation transformer and contain independently controlled inverse parallel electronic switches for each of the (7) taps per phase to provide tight voltage regulation.

1.2 Furnished with Equipment

  1. Factory Test Report
  2. Protective Packaging
  3. Installation Drawings
  4. O&M Manual
  5. Warranty Statement

1.3 Documents & Standards

National Electrical Code, NFPA 70-2005; NEC Article 250-5d.

American National Standards Institute (ANSI).

IEEE C2: Comply with IEEE C2.

IEEE c57.12.91: Comply with IEEE C57.12.91 Test Code for Dry Type Distribution and Power Transformers (ANSI).

IEEE c62.41: Recommended Practice on Surge Voltages in Low Voltages AC Power Circuits (ANSI).

NEMA 250-91: Enclosure of Electrical Equipment.

Occupational Saftey & Health Act (OSHA).

Local Codes & Authorities having jurisdiction for this installation.

1.4 System Description

1.4.1 The GSR is designed to maintain constant voltage and power line conditioning to the equipment load under a wide variety of conditions, even when the utility input voltage, frequency, or system load vary widely. The GSR shall consist of an all copper, multiple tapped, triple shielded isolation transformer and contain independently controlled inverse parallel electronic switches for each of the (7) taps per phase to provide tight voltage regulation. The phase current shall be monitored for zero current recognition to initiate any required tap change. Linear devices shall be used for line synchronization to prevent phase shift errors normally associated with simple CT zero current crossing acquisition. The system shall be microprocessor controlled.

1.4.2 The GSR shall be of a solid state electronic tap switching design that shall comply with UL 1012 for the intended application. Output impedance shall be 3.0 to 5.0 percent, depending on the kVA rating.

1.4.3 The GSR shall be manufactured such that it will maintain electrical properties, even under severe overload, under/over voltage and under/over frequency conditions. Input correction shall be -30% to +20% of nominal input voltage.

1.4.4 The system design shall be capable of operating at an input frequency range of -15% to +10% of nominal, without clearing protective devices or causing component failure within the GSR. The GSR transformer winding shall be continuous copper with electrostatic triple shielding and K-13 rated for the purpose of handling harmonic currents.

1.4.5 The GSR shall be a single module rated to supply the full load as specified herein. A (N+X) paralleled GSR system shall be utilized for accomplishing redundancy. A redundant GSR system shall have each module rated to supply a full load as specified.

1.5 System Operation

1.5.1 Normal:

1.5.2 Input Power Disturbance: If the input voltage or frequency exceeds programmable minimum or maximum set points for a programmable time period (Factory Set – 10 Seconds), the GSR shall electronically shut down. When electrical parameters are back within acceptable limits for a programmable time period (Factory Set – 60 Seconds), the GSR shall automatically restart and continue to provide conditioned power to the load.

1.5.3 Output Power Disturbance: If the output voltage exceeds the acceptable programmable limits, the GSR shall automatically shut down. Operation won’t automatically resume and require a manual restart.

1.6 Quality Assurance

1.6.1 The manufacturer shall have a Quality Assurance (QA) program in place with inspection of incoming parts, modular assemblies, and final products. The manufacturer shall have a designated QA manager who is responsible for overseeing the overall QA process, as well as, Quality Control (QC) representatives  responsible for actively overseeing the manufacturing process.

1.6.2 A final test procedure for the product shall include a check of all performance specifications and a minimum “burn in” period. An on-site test procedure shall include a check of controls and indicators after installation of the equipment.

1.6.3 Storage, Handling, & Delivery: The equipment shall be shipped on a wooden pallet suitable for forklift handling. The equipment shall be covered with clear plastic sheeting to prevent dust and dirt from entering the unit during shipment. For international shipment, a wooden pallet will be constructed of treated wood and shall meet all other specifications required for international freight.

1.7 Submittals

1.7.1 Proposal: Catalog cut sheets and/or data sheets describing the proposed equipment shall be submitted with the proposal. A users listing shall be available upon request giving company names, locations, and systems installed. All deviations from this specification shall be listed and included with the proposal.

1.7.2 Receipt of Order: A minimum of two sets of installation drawings showing outline dimensions, weights, connections, and a one-line diagram of the GSR shall be sent to the purchaser to be used in planning the installation of the system.

1.7.3 Formal Approval: If a formal submitted approval is required for the project then the following should be requested, submitted, and approved before design/construction of the GSR commences:

  1. Equipment Installation Outline
  2. External Cabling Connection Diagram
  3. Equipment One-Line Power Diagram
  4. Equipment Elevation Drawing
  5. “Other” Site Evaluation Diagrams

1.7.4 Delivery of Equipment: As a minimum, the following shall be provided with the equipment upon its arrival to the final destination:

  1. Operation & Maintenance Manual
  2. System Installation Procedures
  3. System Operation Procedures
  4. System Troubleshooting Instructions
  5. System Maintenance Milestones
  6. Recommended Spare Parts List
  7. Final Test Report Copy

1.8 Warranty

1.8.1 The manufacturer shall state the warranty of the equipment, and in no case shall it be less than 12 months after start-up or 18 months after shipment, whichever occurs first. A warranty statement will be provided with the equipment and included as part of the overall O&M manual.


2.1 System Size

2.1.1 The GSR will be sized to handle any application up to 1,500kVA.

2.2 GSR Input

2.2.1 Input Voltage: 208, 440, 460, 480, or 600 Volts at 60Hz and 208, 380, 400, 415, or 600 Volts at 50Hz. These three phase input voltages are available in 3-wire (DELTA) or 4-wire (WYE) configurations.

2.2.2 Voltage Range: +20% to -30% of Nominal.

2.2.3 Frequency: [50Hz or 60Hz].

2.2.4 Input Current THD: Complies with IEEE 519.

2.3 GSR Output

2.3.1 Output Voltages: 208, 440, 460, 480, or 600 Volts at 60Hz and 208, 380, 400, 415, and 600 Volts at 50Hz. These three phase output voltages are available in 3-wire (DELTA) or 4-wire (WYE) configurations.

2.3.2 Frequency: [50Hz or 60Hz].

2.3.3 Operating Frequency: The GSR shall be capable of operating at +10% to -15% of the nominal frequency, 50Hz or 60Hz, with programmable high and low limits to alarm and electronically shut down the GSR. Limits shall be set to +/-2Hz from nominal and electronic shutdown shall occur if limits are exceeded for 10 seconds. Once back within limits for a programmable time period of 60 seconds, the GSR shall automatically restart.

2.3.4 Response Time: The GSR shall respond to any line voltage variation in 1/2 cycle while operating linear or nin-linear loads, with a load power factor of 0.60 of unity. Peak detection of the voltage sine wave shall not be permitted to avoid inaccurate tap switching due to input voltage distortion.

2.3.5 Line Voltage Regulation: Output regulation shall be +5%, -6%, given an input voltage variation of -30% to +3% of nominal, when within +/-5% of the nominal frequency.

2.3.6 Correction Time: The GSR output voltage shall be corrected to within +5%, -6% or less within 1 cycle per tap for an under voltage condition. For an over voltage condition, the output shall correct within 1 cycle directly to the appropriate tap without stair-casing intermediate taps. Typical correction time shall be 1 to 2 cycles.

2.3.7 Load Regulation: No load to full load regulation shall be 3% typical under linear loading. The GSR shall be adjusted so that the combination of line voltage regulation and linear load regulation results in a maximum output voltage variation of +7% to -8% from nominal, when within +/-5% of the nominal frequency.

2.3.8 Efficiency: Operating efficiency shall be a minimum of 96%, typical at full load.

2.3.9 Noise Level: Transverse-mode noise attenuation shall be 3dB down to 1000Hz and 40dB down per decade to below 50dB with a resistive load. Common-mode noise attenuation shall be 140dV or greater.

2.3.10 Overload Capacity: 200% (10 Seconds), 500% (1 Second), & 1000 (1 Cycle).

2.4 Environmental

2.4.1 The equipment shall be suitable for installation indoors (altitude 0 to 12,000 meters or 0 to 4,000 feet) with ambient temperatures ranging from 0° to +40°C (32° to +104°F) with 1% de-rating for each 1°C above 40°C up to 50°C, and relative humidity from 0% – 95% non-condensing.

2.4.2 Site Conditions:

  1. Ambient: 0° to 40°C (32° to 104°F) with 50° and 55° (Optional).
  2. Humidity: 0% to 95% Non-condensing.
  3. Audible Noise: <150kVA (40-50dB), 225-500kVA (50-60dB), 625-1000kVA (65dB).
  4. Construction: Suitable for indoor application. Outdoor enclosures (Optional).
  5. Service Factor: Continuous duty, 24-hour service.

2.5 Access Requirements

2.5.1 The GSR shall have removable panels on the front, rear, and sizes as required for ease of maintenance and/or repair. Only one side of the unit shall require access for the replacement of control circuit boards and solid-state switching devices. Electrical input and output termination shall be top, side or rear access, depending on the kVA rating, with the input termination made to the terminals provided, copper standoff bus or directly to the main input circuit breaker terminals and ground bus. The output termination shall be made to the terminals provided or copper standoff bus, depending on the kVA rating.

2.6 Input Over Current Protection

2.6.1 The GSR shall be provided with an integral,  three pole, molded case, manually operated, thermal magnetic input circuit breaker rated at 125% of the full load input current. In addition, the system input current – Phase A,B, and C shall be monitored and digitally displayed. A programmable over current alarm shall be provided.

2.7 Bypass Switch

2.7.1 The GSR shall be provided with an integral break before make rotary bypass switch. The GSR shall be either on line or bypassed with one turn on the switch. On models where the input and output nominal voltages are different, a regular bypass shall be provided, in which the shielded isolation transformer will remain on line to provide voltage transformation and isolation. On models where the input and output nominal voltages are the same, an integral break before make rotary maintenance bypass switch shall be provided to wrap around and isolate the GSR. In this case, an input neutral conductors shall be provided and the bypass switch shall bypass with output neutral, as well as, the phase conductors. The bypass switch circuitry shall be wired such that it cannot switch the unregulated power directly to the active load. Bypass switch actuation shall trip the GSR input breaker, so that the facility load must then be reconnected using the input breaker.

2.8 Alarms

2.8.1 The GSR shall be provided with an input over/under voltage, input over current, over/under frequency, voltage phase reversal, voltage phase imbalance, output over/under voltage, and output over current alarms. The alarms shall automatically reset upon return to nominal operating conditions. Remote communication of alarms via a contact closure shall be provided. Optional digital communication via RS232 and RS485 shall be made available.

2.8.2 Indicators: The GSR shall be provided with individual “Fuse Failure” indicator lights, Phase A,B, and C on the front panel for diagnostic purpose. Failure of either fusible links or phase semiconductor fuses shall be indicated. The GSR shall be equipped with both an “Output Failure” and “Over Temperature” indicator light on the front of the enclosure to indicate an over temperature condition or an output over/under voltage condition, not caused by the input voltage or frequency being out of range. An input “Input Out of Range” indicator light shall be provided on the meter face to indicate that the input voltage or frequency has exceeded acceptable limits.

2.9 Metering

2.9.1 A digital input meter shall be provided to display line voltages, line currents, frequency, kVA, kW, and power factor. A separate digital output meter shall be provided to display line to line voltages, line to neutral voltages, phase currents, and neutral current. Both meters shall have programmable minimum and maximum value set points, recorded in EEPROM. Both meters shall be capable of optional remote communications via RS232 and RS485.

2.10 Input & Output Cable Connections

2.10.1 The GSR shall have provisions for the installation of cable lugs directly to the input/output bus bars or conductors to the input/output terminals provided. The manufacturer shall allow sufficient space for up to ____ copper conductors per phase and for the neutral bus or terminal. The GSR shall have provisions for the installation of cable lugs directly to the ground bus bar or conductor to the terminal provided. The manufacturer  shall allow sufficient spacing for ___ copper grounding conductors.

2.11 Enclosure & Ventilation

2.11.1 The GSR enclosure shall be painted welded steel or reinforced riveted galvanized frame construction in accordance with NEMA 1 class specifications. The GSR isolation transformer shall be designed for convection cooling. If fan cooling is required for the solid-state electronic switching devices, air filters shall be provided to mitigate dust infiltration.

2.12 Output Transient Suppression Network

2.12.1 Three phases, using high-energy solid-state components with 5-nanosecond maximum response time and a coordinated RC filter network. Connections shall be made at GSR output terminals. The GSR shall provide Transient Voltage Suppresssion (IEEE std. 587, Categories A & B, UL 1449). An input Transient Voltage Surge Suppressor (TVSS) shall be provided external to the GSR to divert high-energy voltage spikes and increase system reliability and life. The input transient suppression (TVSS) shall remain in the circuit when the GSR is in maintenance bypass.

2.13 Automatic Controls

2.13.1 The control portion of the cabinet containing the circuit boards and connection to the semi-conductor devices shall be separate from the transformer and input/output terminations. Each phase shall be regulated using a single microprocessor controlled circuit board, which shall be interchangeable between phases. A single circuit board shall be interchangeable in units rated 10kVA to 50kVA and another single  control circuit board shall be interchangeable in units rated 75kVA to 1,000kVA allowing for ease of service. Once shipped from factory, the GSR should not require adjustments of its controls to regulate within specifications.

2.14 Transformer Component

2.14.1 Comply with UL 1561, including requirements from non-sinusoidal load-current-handling capability to the degree defined by the designated K-factor.

2.14.2 Cores: Grain oriented, 6 grade, stressed relieved, non-aging silicon steel.

2.14.3 Coil Insulation: 200 degrees C class.

2.14.4 Temperature Rise: Designed for 115° C maximum rise above a 40° C ambient.

2.14.5 Output Impedance: 3.0 to 5.0 percent.

3.14.6 Regulation: 2.5 to 4.0 percent maximum at full-resistive load; 6 percent maximum at rated nonlinear load.

2.14.7 Full Load Efficiency: 96% to 98% at rated nonlinear load.

2.14.8 Magnetic field strength external to transformer enclosure less than 0.1 Gauss at 450mm.

2.15 Construction

2.15.1 Quality: All materials, parts, and components used will be new and of the highest grade. Brackets and securing hardware shall be electroplated with corrosion resistant material. Internal wiring conductors shall be combined into cables, or bundles and shall be tied securely together.

2.15.2 Design: The system shall use components of adequate rating to provide an expected service life of twenty (20) years continuous duty and ten (10) years without component replacement, provided that routine maintenance procedures are carried out.

2.15.3 Experience: The manufacturer should have at least (10) years experience designing, constructing, and servicing isolation transformer systems.

2.15.4 Maintainability: No regular maintenance service operations are required, under nominal environment conditions, except for a yearly Preventative Maintenance (PM) review. Maintenance may be done at more frequent intervals if desired.

2.15.5 System Layout: Modules and subassemblies shall be mounted in open construction design so that each may be easily replaced. The equipment shall be constructed so that each component can be replaced without the need for specialized tools.

2.15.6 Installation: Contaminants such as magnetic, metallic, conductive, abrasive, or chemically active materials must be avoided in the airflow by effective filtering. Materials such as dust or lint, which can accumulate and block ventilation passages, must also be filtered.

2.16 Optional Features

2.16.1 Outdoor Rated Enclosure – The DTS will be built to endure the harshest outdoor environments – sand, snow, rain, salt, etc. The enclosures will be built to NEMA 3, 3R, 4, 4X, 12… standards. For large systems (300kVA +) or “turn-key” applications the SFC can be built into an ISO container footprint allowing for easy transportation, installation, and maintenance.


3.1 Manufacturing

3.1.1 The manufacturer shall design, build, test, and arrange for shipment of the DTS if requested by the customer.

3.1.2 The manufacturer shall prepare and deliver the required drawings and manuals with the equipment.

3.2 Site Preparation

3.2.1 The owner shall prepare their site for installation of the equipment.

3.2.2 The owner shall arrange for local electricians to install the equipment.

3.2.3 The DTS shall be installed in accordance with local codes and the OEM’s recommendations.

3.3 Field Service Start-up & Inspection

3.3.1 The DTS is to be checked and inspected by the field service representative from the OEM to confirm proper installation.

3.3.2 The DTS is to be started-up by the field service representative from the OEM to confirm proper operation. The OEM representative should provide commissioning, training, etc. if requested.