# Preliminary Design of the Electrical Power Systems for DTT Nuclear Fusion Plant
## 2 DTT Power Plant
### Load Classification  
An adequate survey of the electrical loads is necessary to preliminarily define the electrical distribution configuration, cable characteristics and other equipment design.  
Electrical loads can be classified mainly according to the following criteria:  
1. Power profiles, leading to two possible types of load: 1. Steady-state loads: Characterized by a continuous load profile (i.e., constant or quasi-constant load with slow variations). 2. Pulsed loads: Characterized by an intermittent load profile, a very high value of load (comparable to the rating of the equipment) and very sharp variations; this kind of load could imply severe effects on the whole electrical network, such as very deep voltage sags and load disconnections.
2. Power supply reliability, classified according to the following categories: 1. Ordinary loads (OLs): Loads related to the normal operations of the processes and utilities; the lack of their power supply does not impair the safety of the personnel and does not cause damages to the plant. The national grid constitutes the normal (or main) power supply. 2. Investment Protection (IP) loads: Essential loads related to keeping alive the essential services of the plant (e.g., air conditioning, fire-fighting, cooling water, etc.) and to avoiding extensive damages to the plant in the case of sudden loss of the main power supply. These loads may accept an interruption in the power supply of at least 90 s; in the case of sudden loss of the main power supply, they will be fed by the emergency power generation. 3. Safety Important Class (SIC) loads: Vital loads related to the safety of the personnel, to the protection and continuous monitoring of the plant and to the safe shut down of the equipment in order to avoid potential incidents in the case of sudden loss of power supply. These loads will be uninterruptedly fed by the AC UPSs and DC UPSs.  
To allow a smooth design process of the electrical distribution system, all electrical loads are characterized according to the above-mentioned criteria and categories and  
Figure 1: DTT estimated load profile compared with the connection request to the national grid. The dashed line shows the contribution of the baseload that is practically constant during the entire operation cycle.  
collected in an Electrical Load List (ELL), a database clustering the loads as functional macro-areas, in a Plant Breakdown Structures (PBS) [16].  
For each load, the following relevant information is indicated:  
* Location: The building where the load is located.
* Load profile: Steady state or pulsed.
* Voltage at the terminals.
* Load Class: OL, IP or SIC.
* Type of power supply, depending on whether the load is powered only by the national grid (normal load) or also by the Emergency Diesel Generator (EDG) or by the Uninterruptible Power Supply system (UPS).
* Power factor.
* Power absorption in terms of active and apparent power, measured in MW and MVA, respectively (only peak values are reported).
* Load center: The distribution substation to which the load is connected.  
The number of PBS currently identified for DTT is ten; they are listed in Table 1, which also provides a short description for each of them.