2. In this Schedule—
“climatic environments” means the conditions in which relevant instruments may be used;
“critical change value” means the value at which the change in the measurement result is considered undesirable;
“disturbance” means an influence quantity having a value within the limits specified in the appropriate requirement but outside the specified rated operating conditions of the relevant instrument. An influence quantity is a disturbance if for that influence quantity the rated operating conditions are not specified;
“f” means the frequency of the voltage supplied to the relevant instrument;
“fn” means the specified voltage reference frequency;
“I” means the electrical current flowing through the relevant instrument;
“Imax” means the maximum value of I for which the error lies within the MPEs;
“Imin” means the value of I above which the error lies within maximum permissible errors (MPEs) (polyphase relevant instruments with balanced load);
“In” means the specified reference current for which the transformer operated relevant instrument has been designed;
“influence quantity” means a quantity that is not the measurand but that affects the result of measurement;
“Ist” means the lowest declared value of I at which the relevant instrument registers active electrical energy at unity power factor (polyphase relevant instruments with balanced load);
“Itr” means the value of I above which the error lies within the smallest MPE corresponding to the class index of the relevant instrument;
“measurand” means the particular quantity subject to measurement;
“MPE” means the maximum permissible error value as set out in paragraph 15;
“PF” means power factor = cosφ = the cosine of the phase difference φ between I and U;
“rated operating conditions” means the values for the measurand and influence quantities making up the normal working conditions of a relevant instrument;
“U” means the voltage of the electricity supplied to the relevant instrument; and
“Un” means the specified reference voltage.