The Megger Three-Phase TTR® Test Set (Catalog No. 550503) is a fully automatic, self-checking, and self-calibrating, menu-driven instrument designed for measuring the turn ratio, phase shift, and excitation current of power, distribution, and instrument transformers. A "-47" suffix in the catalog number (550503-47) indicates a 230-V input power supply, as opposed to the standard 120-V supply. The test set is housed in a sturdy plastic case with a lid and carrying strap, and the inside bottom half of the case is nickel coated. A canvas carrying bag is provided for accessories.
Function Description:
The Three-Phase TTR Test Set is capable of testing both single-phase and three-phase transformers, with or without taps, in accordance with IEEE C57.12.90 – 1997 standards. For three-phase measurements, the test set connects to all three phases of the transformer under test. Its lead selection circuitry allows for automatic measurement of all phases without requiring changes in connections, eliminating the need for hook-up charts during three-phase transformer testing. The instrument displays turn ratio, phase shift, and excitation current readings on a large LCD. The measurement of transformer excitation current and phase shift angle helps in detecting shorted turns or an unequal number of turns connected in parallel. The device also provides operating condition (error) messages to identify incorrect test connections, abnormal operating conditions, or winding problems. Test results can be saved, printed using an optional printer, or uploaded to a personal computer (PC) for full transformer test reports.
Important Technical Specifications:
Electrical:
- Input Power:
- Cat. No. 550503: 120 V ac ±10%, single phase, 50 ±2 Hz or 60 ±2 Hz, 100 VA (IEC 1010-1 installation category II)
- Cat. No. 550503-47: 230 V ac ±10%, single phase, 50 ±2 Hz or 60 ±2 Hz, 100 VA (IEC 1010-1 installation category II)
- Pollution Degree: Designed for Pollution Degree II.
- Protective Devices:
- Fuses (2)*:
- Cat. No. 550503: Type T, 250 V, 1A (IEC 127 designation)
- Cat. No. 550503-47: Type T, 250 V, 0.5 A (IEC 127 designation)
- High voltage and low voltage measurement circuit shorting relays.
- Heavy duty varistors, transient voltage suppressors, and gas surge voltage protectors.
- *Two spare fuses are included with each TTR as spare parts.
- Output Test Voltage and Current:
- 3 test voltages: 80 V rms, 40 V rms, 8 V rms.
- Current: up to 500 mA.
- Test Frequency: Same as line frequency.
- Loading of Test Transformer: Less than 0.2 VA.
Measuring Ranges:
- Turn Ratio:
- 80 V ac: 0.8 to 45,000 (5-digit resolution)
- 40 V ac: 0.8 to 25,000 (5-digit resolution)
- 8 V ac: 0.8 to 8,000 (5-digit resolution)
- Current: 0 to 500 mA (3-digit resolution)
- Phase Deviation: ±90 degrees (1 decimal point for minutes display, 2 decimal points for degree display, 2 decimal points for centiradian display)
Accuracy:
- Turn Ratio:
- 80 V ac: ±0.1% (0.8 to 2000), ±0.15% (2001 to 4000), ±0.25% (4001 to 10000), ±0.3% (10001 to 45000)
- 40 V ac: ±0.1% (0.8 to 2000), ±0.15% (2001 to 4000), ±0.3% (4001 to 10000), ±0.35% (10001 to 25000)
- 8 V ac: ±0.1% (0.8 to 2000), ±0.25% (2001 to 4000), ±0.35% (4001 to 8000)
- Current (rms): ±(2% of reading + 1 digit)
- Phase Deviation: ±3 minutes
Usage Features:
- Fully Automatic Operation: Simplifies testing procedures.
- Self-Checking and Self-Calibration: Performs checks at power-up and calibrates at each measurement for accuracy.
- User-Friendly Interface: Menu-driven operation with a large, easy-to-read LCD that displays alphanumeric data.
- Comprehensive Measurements: Measures turn ratio, phase shift (in degrees and centiradians), and excitation current.
- Versatile Testing: Capable of easily measuring regular windings, tertiary windings, and Current Transformers (CTs).
- Data Storage: Stores up to 200 tests for retrieval, printing, or uploading to a PC.
- Custom Settings: Allows saving up to 9 custom transformer settings for faster and easier testing.
- Polarity Check: Checks for reverse polarity at the start of each test.
- Y2K Compatible: Includes Y2K compatible date setting.
- Reporting: External printer records test data, and an external PC or laptop can be connected to transfer test results and generate full transformer test reports.
- Quick Test Mode: Provides the fastest testing of a transformer.
- Standards Compliance: Tests to ANSI, IEC, or Australian standards.
- Lead Markings: Leads are marked according to ANSI, IEC, and Australian standards.
- Multilingual Support: Choice of six languages.
- Environmental Robustness: Meets the requirements of both the European EMC and Low Voltage Directives, ensuring trouble-free operation in switchyards under electrostatic and magnetic interference conditions.
Maintenance Features:
- Fuse Replacement: The instrument's control circuits are protected by two mains circuit fuses, which are user-replaceable. Specific fuse types and ratings are provided in the specifications. A warning is issued to disconnect the power input plug before replacing fuses.
- Repair and Component Replacement: To avoid electric shock hazards, operating personnel should not remove the instrument from its case. Any repair or component replacement must be performed by qualified service personnel.
- Technical Support: Megger provides technical support for software and operational assistance.
- Software Updates: Megger periodically provides software updates available for download from their website.
The manual emphasizes safety precautions, including treating all high-voltage terminals as potential electric shock hazards, ensuring proper grounding, and disconnecting test leads from power equipment before handling. It also advises that corrective maintenance should only be performed by qualified personnel familiar with the test set's construction and operation.
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