POWER TRANSFORMER IMPACT RECORDER BASICS AND TUTORIALS

POWER TRANSFORMERS IMPACT RECORDER - IMPORTANCE AND USAGE
What Is The Importance of Power Transformer Impact Recorders During Transport?


There are two types of impact recorders:

· Impact Indicator – is used in all power transformers that are equal or higher than 30MVA and/or of a voltage class equal or higher than 230kV for the domestic market. When the transformer is to be exported, such impact indicator is used in all power transformers that are equal or higher than 5MVA. Four (4) pieces are used, which are fixed to the tank sidewalls.

· Three-dimensional Impact Recorder – is used only when required by the customer and/or by an insurance Company. This reco rder is fixed to the main transformer lid, by means of fastening screws, the nearest possible to its geometrical center. The recorder is turned on before the transformer is loaded by Manufacturer and should remain turned on until the unit is unloaded.

They are intended to indicate whether chocks and vibrations have occurred in th e traver se, longitudinal and vertical directions during the transport, loading and unloading processes. The magnitude of vibration and chocks is recorded in terms of “g” (Multiples of gr avity acceleration), accord ing to TABLE 1.

TABLE 1 – ACCEPTABLE ACCELERATION VALUES DURING TRANSPORT

The ranges of the impact indicator are analyzed after the transformer is unloaded and should be sent back to Manufacturer transformadores. If they have proven to be out of the limits, the Technical Assistance Department will take all necessary steps.

However, if the recommended acceleration limits have been exceeded, it doesn’t mean that damages have occurred to the transformer. If such excess occurs, our technical department should carry out a deeper analysis of the occurrence, defining whether or not an internal assessment or eventually the adoption of another specific action is necessary.

It is necessary to take in account that not only the maximum value is imp ortant, but how many times such value has been reached during the transport.

The following procedures should be followed to turn off and remove the impact recorder:

· Remove the weatherproof protection;
· Check the box sealing for integrity. If damages are found, please report them immediately to Manufacturer
· Remove the box lid. In case of rain, do not allow the penetration of any kind of humidity to the inside of the recorder;
· Turn off the recorder;
· Mark the point where the transport process has been ended;
· Turn the recorder on;
· Close t he box lid;
· Unload the Transforme r;
· Remove the box lid;
· Turn off the recorder;
· Mark the point where the unloading process has been ended;
· Remove the impact recorder’s base from the unit;
· Replace the lid of the recorder box;
· Close the box with the supplied seal and send the impact recorder containing the roll of records to the sales department of Manufacturer, preferably using the same transporting company for return.

IMPORTANT: In case the transport and unloading work is carried out by the same Company, it is not necessary to turn off the recorder and switch its position between one and another operation.

SINGLE PHASE TRANSFORMER POLARITY BASICS AND TUTORIALS

POLARITY OF SINGLE PHASE TRANSFORMERS BASIC INFORMATION
How To Know The Polarity Of Single Phase Transformers?



Single-Phase Polarity
The polarity of a transformer can either be additive or subtractive. These terms describe the voltage that may appear on adjacent terminals if the remaining terminals are jumpered together.

The origin of the polarity concept is obscure, but apparently, early transformers having lower primary voltages and smaller kVA sizes were first built with additive polarity. When the range of kVAs and voltages was extended, a decision was made to switch to subtractive polarity so that voltages between adjacent bushings could never be higher than the primary voltage already present.

Thus the transformers built to ANSI standards today are additive if the voltage is 8660 or below and the kVA is 200 or less; otherwise they are subtractive.

This differentiation is strictly a U.S. phenomenon. Distribution transformers built to Canadian standards are all additive, and those built to Mexican standards are all subtractive. Although the technical definition of polarity involves the relative position of primary and secondary bushings, the position of primary bushings is always the same according to standards.

Therefore, when facing the secondary bushings of an additive transformer, the X1 bushing is located to the right (of X3), while for a subtractive transformer, X1 is farthest to the left.

To complicate this definition, a single-phase pad-mounted transformer built to ANSI standard Type 2 will always have the X2 mid-tap bushing on the lowest right-hand side of the lowvoltage slant pattern.

Polarity has nothing to do with the internal construction of the transformer windings but only with the routing of leads to the bushings. Polarity only becomes important when transformers are being paralleled or banked. Single-phase polarity is illustrated in Figure 2.2.11.

FIGURE 2.2.11 Single-phase polarity. (Adapted from IEEE C57.12.90-1999. The IEEE disclaims any responsibility or liability resulting from the placement and use in the described manner.