- A diagnostic tool for on-site diagnosis of power transformers with on-load tap changer.
- The Transformer Diagnostic System is developed for testing power transformers with an on-load tap changer. The transformer diagnostic system is suitable for pre-failure detection of major degradation mechanisms and defects of different types of on-load tap changers. Winding defects can also be found with this diagnostic system.
The TDS146 is used for:
- Monitoring the contact condition: Condition-based maintenance requires diagnostic measurements to determine when and what kind of maintenance is necessary.
- Diagnoses of the power transformer windings and OLTC in case protective devices have switched off the transformer.
- Measurements after tap changer maintenance or repair:
+ Pre-failure detection of maintenance errors
+ Finding defects that remained undiscovered during inspection (for example contact misalignment).
+ Measurements after tap changer maintenance or repair:
+ Measuring OLTC contact degradation and winding defects inside the transformer tank which are not visible during inspection.
Detection of defects:
The TDS146 checks the main functionality of the tap changer and is able to find such as:
+ Contact deterioration of (for example due to coking or overheating)
Selector switch contacts
Diverter switch contacts
Tap-selector contacts
Change-over selector contacts
Reversing switch contacts
Coarse change-over selector contacts
Fixed-connection contacts
+ Interrupted or damaged transition resistors
+ Mechanical friction in motor drive and transmission
+ Broken or weakened springs
+ Winding damage
+ Maintenance errors
+ Safety contactor for switching time protection
+ Weak or damaged drive axis
+ Synchronization problems between phases
Main functionality of the TDS146:
- Tap changer:
+ Dynamic resistance measurement (DRM)
+ Check contactor for switching time control (if equipped)
+ Position measurement on the OLTC drive axis (for rotor-type OLTCs with accessible drive axis)
+ Motor power measurement on the OLTC drive mechanism
- Transformer windings:
+ Transformer turn ratio measurement
+ DC winding resistance measurement
Relevant standards and recommendations:
- ANSI/IEEE C57.12.90-1987: American national standard / IEEE Standard TestCode for Liquid- Immersed Distribution, Power and Regulating Transformers.
- IEEE Std 62-1995: IEEE Guide for Diagnostic Field Testing of Electric Power Apparatus. Part 1: Oil Filled Power Transformers, Regulators and Reactors.
- IEEE Std C57.12.37-2006: IEEE Standard for the Electronic Reporting of Distribution Transformer Test Data.
- IEEE Std C57.140-2006: IEEE Guide for the Evalua- tion and Reconditioning of Liquid Immersed Power Transformers.
- IEC 60214: Tap-changers - Performance require- ments, test methods and application guide.
- IEC 60076-1: Power Transformers - Part 1: General