**2. Analysis of existing standards applicable to DC operating power supplies**

The following standards are used by the European Telecommunications Standards Institute (ETSI) for the coordination of Telekom stations equipment. These normative documents are required to be applied for DC operation:

• *IEC/EN 60947-2:2009 Low-voltage switchgear and control gear—Part 2: Circuit-breakers*

This standard applies to automated circuit breakers, of which main contacts are intended to be connected to circuits, the rated voltage of which does not exceed 1000 V AC or 1500 V DC; it also contains additional requirements for integrally fused circuit breakers [11].

• SR EN 60947-3:2009 *Low-voltage switchgear and control gear—Part 3: Switches, disconnectors, witch-disconnectors and fuse-combination units*

This standard applies to switches, disconnectors, switch-disconnectors, and fuse-combination units to be used in distribution circuits and motor circuits of which the rated voltage does not exceed 1000 V AC or 1500 V DC. The manufacturer will specify the type, ratings, and characteristics according to the relevant standard of any incorporated fuses [11].

IEC 60947-2 standardizes miniature circuit breakers (MCB) used by the industry. The aforementioned standard creates a frame for power distribution with voltage values of up to 1000 V AC and 1500 V DC for all rated current ranges starting from 0.5 and reaching 6300 A. There are three types of circuit breakers in this class:


An alternative standard for automatic circuit breakers is represented by IEC 60898-1, which refers to the miniature circuit breakers used within the low-voltage AC grids and included in electrical panels from households, shops, or office buildings. **Table 1** synthetizes the major differences between the two standards which apply to MCBs.

Another difference is to be observed when comparing the trigger curves. If the IEC 60898-1 standard clearly describes the B, C, and D curves as depending on the rated

*Micro-Grids - Applications, Operation, Control and Protection*

as shown in **Figure 1**.

c.Environmental protection

b.Reduced total investments: the use of HVDC for the interconnection of two nodes within an electric power system is in many cases the more economical alternative compared to high-voltage alternative current (HVAC) systems

Thus, HVDC systems allow the safe and stable interconnection of AC electrical grids operating at different frequency values, [5], which are otherwise incompatible. In addition, HVDC provides instant and accurate power flow control.

As far as it goes, LVDC microgrid concept has gained the scientific community attention in recent years. A direct current distribution microgrid represents a practical solution to efficiency problems of existing AC electrical grid [6]. While various papers have shown that DC microgrids can play an effective role in solving some operational

**40**

**Figure 2.**

**Figure 1.**

*The key diagram for a mixed microgrid with separate AC and DC rings.*

*Cost versus transmission distance for HVDC and HVAC systems [4].*

### *Micro-Grids - Applications, Operation, Control and Protection*


#### **Table 1.**

*Comparison between the characteristics of miniature circuit breakers (MCBs) regulated according to IEC [12].*

#### **Figure 3.**

*Examples of Resi9 circuit breakers for residential applications and Eazy9 for industrial use manufactured by Schneider [13].*

current, IEC 60947-2 shows that instantaneous triggering may be adjustable in accordance to the user's necessities or predefined by the manufacturer with a precision of 20%. This is the reason why many manufacturers have added K, Z, and MA curves (**Figure 3**).

In conclusion, the use of MCBs which are certified according to both standards and are suitable for residential as well as industrial use is preferable.

#### • *IEC/EN 60269-1 Low-voltage fuses—Part 1: General requirements*

This standard is applicable to fuses incorporating enclosed current-limiting fuse links with rated breaking capacities of not less than 6 kA, intended for protecting power-frequency AC circuits of nominal voltages not exceeding 1000 V or DC circuits of nominal voltages not exceeding 1500 V.

**43**

*Assessment of the Main Requirements and Characteristics Related to the Implementation of…*

• *IEC/EN 61000-4-29 Electromagnetic compatibility (EMC)—Part 4–29: Testing and measurement techniques—Voltage dips, short interruptions and voltage* 

• *IEC/EN 61000-4-5 Electromagnetic compatibility (EMC)—Part 4–5: Testing and* 

As mentioned by [14], in the United States, restrictions regarding electrical systems are established by the requirements of NEC (NFPA-70), Section 210.6, for branch-circuit voltage limitations. Thus, this code from the US National Electrical Code imposes the voltage in residential and similar occupancies to 120 V, while only

Also, at the moment, an IEEE standard for DC microgrids for rural and remote electricity access applications is under development, targeting sustainable DC off-

**3. Assessment of consumption requirements and preliminary features for the development and implementation of residential DC microgrids**

In order to establish the proper methods regarding the consumers' adaptability to a DC grid, it is necessary to identify the ones which are to be used and to analyze the possibilities of modifying the included power supply. The classification of electrical appliances that are usually found in a household is therefore highlighted.

• Heating appliances with resistive loads only (hotplates, ovens, radiators, heat exchangers) can easily be supplied from the DC grid if the same voltage level and electric power requirements are ensured as from the single-phase AC grid. If the DC voltage is different from the end users' parameters, buck (step-

• Household appliances with inductive loads (fridge, pumps, vacuum cleaner, fans, etc.) using mainly asynchronous AC motors require DC/AC inverters in order to restore the pure or modified sine wave which drives the electric motors.

• Equipment with multiple (resistive, inductive) loads: washing machines and HVAC equipment (air conditioning, ventilation/heating) which operate by using a DC/AC inverter in order to adapt the required operating parameters. These household appliances also include elements that can be DC power supplied, but the required separation of the DC and AC paths is difficult and not justified.

• Low-power equipment using DC in the voltage range of 5–48 V. These can operate with step-down DC/DC converters. A separate 48–50 V power supply line can be used for a low installed power supply for the following end users: LED, laptop/desktop PCs, telecommunication equipment (router, mobile

A step-down converter with 48 V input and 5–9–12–20–24 V output operates with very good conversion efficiency. Due to the fact that it does not process signifi-

**3.1 Methods for adapting the electrical consumers to DC grid parameters**

The main categories of electric consumers can be defined as follows:

down) or boost (step-up) DC/DC converters can be used.

phone), LED TV, monitors, printers, etc.

cant power amounts, it has an affordable price.

in the case of specific loads, the limits are raised to 277 V among conductors.

*DOI: http://dx.doi.org/10.5772/intechopen.84413*

*variations on DC input power port immunity tests*

grid and remote power and relying firstly on user's safety.

*measurement techniques—Surge immunity test*

The standard has been updated and released again as SR EN 60269-1:2008/ A1:2010 and SR EN 60269-1:2008/A2:2015.

*Assessment of the Main Requirements and Characteristics Related to the Implementation of… DOI: http://dx.doi.org/10.5772/intechopen.84413*


As mentioned by [14], in the United States, restrictions regarding electrical systems are established by the requirements of NEC (NFPA-70), Section 210.6, for branch-circuit voltage limitations. Thus, this code from the US National Electrical Code imposes the voltage in residential and similar occupancies to 120 V, while only in the case of specific loads, the limits are raised to 277 V among conductors.

Also, at the moment, an IEEE standard for DC microgrids for rural and remote electricity access applications is under development, targeting sustainable DC offgrid and remote power and relying firstly on user's safety.
