Appliance blocking

Appliance blocking is a technical measure preventing the switching of appliances during high tariff periods. It is used with electrical heating systems and boilers. It prevents these appliances from switching on. The customers save money this way, since electricity is more expensive during high tariff periods.

Distribution system

The distribution system is a set of facilities for the distribution of electricity from the transmission system (or from sources connected to it) to end-users. The distribution system includes the control, protective, safety and information systems. For Czech Republic electricity grid conditions, this concerns equipment with voltages of 110 kV and lower.

Electrical energy

A form of energy utilized by means of electromagnetic fields. Usually referred to as electricity. For direct current, electricity is defined as follows:

W = U * I * t
 
U - Voltage (in Volts),
I - Current (in Amperes),
t - Time period (in hours).

The product of U * I gives us the electrical output (in Watts). If the network voltage is 230 V and we consume 2 A of electricity for the duration of 5 hours (230 * 2 * 5) we consume 2300 Watt hours, usually recorded in the form 2.3 kWh (kilowatt hours).

Electricity grid

A system ensuring the production, transmission, distribution and end usage of electricity. Some definitions exclude the electricity consumption subsystem from this system. Apart from the main production, transmission and distribution facilities, which form the backbone of the system, the electricity grid includes a range of other elements providing for measurement, protection, inspection and control.Electrical networks are the main elements ensuring the continuous distribution of electricity within the electricity grid. As well as these, there is also an information system providing for regulation and control of the system. The electricity grid is currently a highly centralized system with sophisticated management methods.

Electricity

General term, synonymous to "electrical energy".

Energy

There are the following types of energy:

• mechanical energy,
• thermal energy (heat),
• chemical energy,
• energy of physical bonds,
• electromagnetic energy,
• electrical energy (electricity).

Energy is measured in Joules. A Joule is the energy corresponding to work done by a force of 1 Newton on a 1-meter trajectory.

Ripple control

Ripple control is a set of devices that serve for the control (switching) of appliances (electrical heating, cooling, irrigation etc.). The control is performed by means of transmitters placed in distribution points and receivers installed in the premises of the customer. The control signal is transferred by means of signals sent across distribution system power lines. Individual types of appliances are distinguished by various forms of these signals. Ripple control is a significant instrument for controlling network load.

Protected customer

A protected customer is an individual or a corporation entitled to connection to a distribution system and to supplies of electricity of a determined quality and at regulated prices.

Circuit breaker

The main circuit breaker by the electricity meter is a device protecting your end-user place of consumption. It is usually located in the vicinity of the electricity meter and it can be used to switch off electricity supplies for the entire place of consumption. The circuit breaker must conform to ČSN EN 60898 or ČSN EN 60947 standards with "B" shut-off characteristics. If an appliance with high starting current is used, a "C" type circuit breaker may be used. If circuit breakers with an adjustable short-circuit release are used, these circuit breakers have to be modified in order to provide for the possibility of sealing the chosen setting. In the case of such a modification not being possible, the customer's monthly payments will be calculated from the highest setting of the circuit breaker. In substantiated cases, the supplier can allow for the usage of a "D" type circuit breaker conforming to the above-mentioned standards. The breaker element has to be labeled with a unique current rating designation (for example by means of a special color of the control lever). If the circuit breaker was appropriately installed and registered by the supplier in an application or Electricity consumption contract prior to July 1, 2001, its shut-off characteristics may differ from those listed above. The supplier is entitled to verify whether the main circuit breaker by the electricity meter conforms to the appropriate technical standard. Circuit-breakers are is rated in amperes (A).

Kilowatt-hour (kWh)

One kilowatt-hour is the amount of electricity consumed by:

• a 100 W light bulb in 10 hours,
• a 15 kW direct heating electrical boiler in 4 minutes,
• a 3 kW electrical storage stove in 20 minutes.

Network voltage

Voltages used for classification of electrical networks and in the construction of electrical devices and appliances. Degrees of voltage are defined as voltage between wires (i.e. in multi-phase systems by means of delta voltage). The following voltage degrees are used in the Czech Republic:

• safe voltage up to 50 V incl. - abbreviation sv
• low voltage from 50 V to 1000 V incl. - abbreviation lv
• high voltage from 1000 V to 52 kV - abbreviation hv
• very high voltage from 52 kV to 300 kV - abbreviation vhv
• especially high voltage from 300 kV to 800 kV incl. - abbreviation ehv
• ultra high voltage above 800 kV- abbreviation uhv

The "high voltage" category is sometimes used in specialist literature to designate of all voltage degrees above 1000 V.

Voltage deviation

Voltage deviation is the difference between voltage at a given point in the network and a  referential voltage value, such as rated voltage, mean value of working voltage or contracted voltage. The difference is usually given in percent.

Combinations of major fluctuations of current in appliances and high impedance of the distribution network can cause major variations in supply voltage. Electricity supplies are considered of sufficient quality when the fluctuations don't fall outside an agreed area of tolerance.

Consumption location

Consumption location is the point of connection of a household (or other real estate (garden, summerhouse, cottage, garage etc.) to the electricity network. The customer has as many electricity supply contracts as he/she has places of consumption. Completely different terms and billing may apply for each place of consumption.

An consumption location is defined as an electrical consumption facility of a single consumer in a self-contained and permanently electrically wired unit, located on a continuous plot of land, to which electricity is supplied and measured by a single measuring device provided by the supplier.

Authorized customer

This designates an electricity consumer authorized by law to enter into an electricity consumption contract with a supplier of one's own choosing. An authorized (also referred to as eligible) customer is usually limited by annual electricity consumption.

Transmission system

A system of facilities for the transmission of electricity, including control and information systems.

Power surge

A voltage higher than the highest allowed working voltage (maximum voltage for a given device). Power surges in the electricity grid occur as a result of manipulations and changes accompanied by transitional effects (for example a so-called switching surge), as a result of resonance or as a result of external effects (atmospheric power surges). Electrical appliances are usually designed to withstand certain levels of power surges for a given amount of time. It is necessary to protect appliances from surges that could damage them, for example by utilizing lightning rods, earth-wires, dischargers and surge diverters.

Surge protection

Surge protection is a device preventing or limiting the occurrence of surges and eliminating its effects. It becomes effective when voltage in the electricity grid exceeds given values.

The simplest forms of surge protections consist of individual elements that can be grouped under the common heading of protective elements, so-called surge diverters. They are:

• protective dischargers,
• lightning arresters,
• diacs, triacs, thyristors, Zener diodes, avalanche diodes, suppressor diodes and special fast semiconductor elements,
• and the recently almost exclusively used metal oxide (ZnO) varistors.

Rate

A rate is the part of the price list that sets the prices and terms for electricity supplies. There are double-tariff rates (making it possible to utilize beneficial prices in periods of low overall electricity consumption - the so called low tariff) or single-tariff rates, which do not have this advantage.

Low tariff (LT)

Low tariff is a time band when there is a lower load on the electricity distribution network. During this period, electricity production costs are usually lower. Electricity companies thus motivate customers to consume electricity during these periods by offering it for reduced prices. Because the pattern of electricity usage changes throughout the year, the time period of the low tariff can change accordingly, based on the chosen rate. In particular, the following alternatives can occur:

• low tariff validity period is fixed throughout the year (rate D61),
• low tariff validity period is determined in advance for the duration of three months, it either lasts for 8 or 16 hours a day and stays fixed for a given period. This is referred to as programmed control (rates D24 and D34),
• low tariff validity period may change at any time, however, the supplier is obliged to observe the total duration of the low tariff validity period and the terms of the appropriate rate. This is referred to as operative control.

High tariff (HT)

The high tariff applies outside the period of the low tariff. A higher price is charged for electricity consumed during this period.